This answer meets the requirement of configuring one connection as Active for both ingress and egress traffic, and enabling automatic failover to the passive connection in case of failure. The reason is:
The advertised route priority is a value that Cloud Router uses to set the route priority when advertising routes to your on-premises router. The lower the value, the higher the priority1. By setting the advertised route priority as 200 for the active connection, you ensure that it has a higher priority than the passive connection, which has the default value of 1001. This way, your on-premises router will prefer the routes from the active connection over the passive one for ingress traffic.
The MED (Multi-Exit Discriminator) is a value that your on-premises router uses to indicate its preference for receiving traffic from Cloud Router. The lower the value, the higher the preference2. By advertising a lower MED on the active connection from your on-premises router, you ensure that Cloud Router will prefer sending traffic to the active connection over the passive one for egress traffic.
If the active connection fails, Cloud Router will stop receiving routes from it and will start using the routes from the passive connection for egress traffic. Similarly, your on-premises router will stop receiving routes with priority 200 from the active connection and will start using the routes with priority 100 from the passive connection for ingress traffic. This achieves automatic failover without any manual intervention.
Option A is incorrect because setting the advertised route priority > 10,200 on the active connection would deprioritize it globally in your VPC network, which is not what you want1. Option B is incorrect because advertising a lower MED on the passive connection would make Cloud Router prefer sending traffic to it over the active one, which is not what you want2. Option D is incorrect because setting the advertised route priority as 200 for both connections would make them equally preferred by your on-premises router, which is not what you want1.
Reference:
Update the base route priority | Cloud Router | Google Cloud
Configuring BGP sessions | Cloud Router | Google Cloud

The correct answer is D. Create privately used public IP primary and secondary subnet ranges for the clusters. Create a private GKE cluster with the following options selected: --disable-default-snat, --enable-ip-alias, and --enable-private-nodes.
This answer is based on the following facts:
Privately used public IP (PUPI) addresses are any public IP addresses not owned by Google that a customer can use privately on Google Cloud1. You can use PUPI addresses for GKE pods and services in private clusters to mitigate address exhaustion.
A private GKE cluster is a cluster that has no public IP addresses on the nodes2. You can use private clusters to isolate your workloads from the public internet and enhance security.
The --disable-default-snat option disables source network address translation (SNAT) for the cluster3. This option allows you to use PUPI addresses without conflicting with other public IP addresses on the internet.
The --enable-ip-alias option enables alias IP ranges for the cluster4. This option allows you to use separate subnet ranges for nodes, pods, and services, and to specify the size of those ranges.
The --enable-private-nodes option enables private nodes for the cluster5. This option ensures that the nodes have no public IP addresses and can only communicate with other Google Cloud resources in the same VPC network or peered networks.
The other options are not correct because:
Option A is not suitable. Creating RFC 1918 primary and secondary subnet IP ranges for the clusters does not solve the problem of address exhaustion. Re-using the secondary address range for pods across multiple private GKE clusters can cause IP conflicts and routing issues.
Option B is also not suitable. Creating RFC 1918 primary and secondary subnet IP ranges for the clusters does not solve the problem of address exhaustion. Re-using the secondary address range for services across multiple private GKE clusters can cause IP conflicts and routing issues.
Option C is not feasible. Creating privately used public IP primary and secondary subnet ranges for the clusters is a valid step, but creating a private GKE cluster with only --enable-ip-alias and --enable-private-nodes options is not enough. You also need to disable default SNAT to avoid IP conflicts with other public IP addresses on the internet.

When established, Direct Peering provides a direct path from your on-premises network to Google services, including Google Cloud products that can be exposed through one or more public IP addresses. Traffic from Google's network to your on-premises network also takes that direct path, including traffic from VPC networks in your projects. Google Cloud customers must request that direct egress pricing be enabled for each of their projects after they have established Direct Peering with Google. For more information, see Pricing.

https://cloud.google.com/dns/docs/best-practices

This answer meets the requirement of improving the performance of the cache hit ratio associated with the image file. The reason is:
Custom cache keys allow you to control which parts of the request URL are used to build the cache key. The cache key is a unique identifier that Cloud CDN uses to store and retrieve cached content1.
By default, Cloud CDN uses the complete request URL, including the protocol (http or https) and the host (the domain name), to build the cache key. This means that if the same image file is requested from different domains or protocols, Cloud CDN will cache multiple copies of it, which reduces the cache hit ratio1.
By clearing the Host and Protocol checkboxes, you can tell Cloud CDN to ignore these parts of the request URL when building the cache key. This way, Cloud CDN will cache only one copy of the image file, regardless of which domain or protocol it is requested from, which improves the cache hit ratio1.
Option B is incorrect because configuring Cloud Storage as a custom origin backend does not affect the cache hit ratio. It only affects how Cloud CDN retrieves the content from the origin if it is not cached. Option C is incorrect because configuring versioned URLs for each domain does not improve the cache hit ratio. It actually worsens it, because it creates more variations of the request URL that Cloud CDN has to cache separately. Option D is incorrect because configuring the default TTL as 0 for the image file means that Cloud CDN will not cache it at all, which defeats the purpose of using Cloud CDN.
Reference:
Custom cache keys | Cloud CDN | Google Cloud