According to the Juniper Networks JNCIS-SEC Study Guide, when you set up your command-and-control (C&C) category with Juniper ATP Cloud, all of the feeds will initially have zero objects in them. This is normal, as it can take a few minutes for the feeds to download. No action is required in this scenario and you will notice the feeds start to populate with objects once the download is complete.

According to the Juniper Networks JNCIS-SEC Study Guide, when you set up your command- and- control (C&C) category with Juniper ATP Cloud, all of the feeds will initially have zero objects in them. This is normal, as it can take a few minutes for the feeds to download. No action is required in this scenario and you will notice the feeds start to populate with objects once the download is complete.

Explanation
JIMS domain PC probes are a mechanism to obtain username to IP address mapping information from devices in a customer's domain. JIMS initiates a domain PC probe when it receives a request from an SRX Series device for a username to IP address mapping that is not found in the domain security event log. JIMS uses the administrative credentials configured for PC probes to access the device and query the Windows Management Instrumentation (WMI) service for the username to IP address mapping12 References:
1: Juniper Identity Management Service Feature Guide - TechLibrary - Juniper Networks
2: Juniper Identity Management Service (JIMS) Documentation - Juniper Networks

Explanation
B: Chassis cluster member devices synchronize configuration using the control link. The control link is used to exchange control messages and configuration information between the two nodes of a chassis cluster1. The primary node pushes the configuration to the secondary node and ensures that both nodes have the same configuration2.
C: A control link failure causes the secondary cluster node to be disabled. If the control link fails, the primary node cannot communicate with the secondary node and assumes that the secondary node is down1. The primary node then disables the secondary node and takes over all the traffic processing2.
E: Heartbeat messages verify that the chassis cluster control link is working. The control link also carries heartbeat messages that are exchanged between the two nodes every 500 milliseconds by default1. The heartbeat messages indicate the status and health of the nodes and the control link2.
A: Chassis cluster control links must be configured using RFC 1918 IP addresses. This is a false statement. The control link can use any IP address range as long as it is not in conflict with other interfaces or routes on the cluster nodes1. RFC 1918 IP addresses are private addresses that are not routable on the Internet4.
D: Recovery from a control link failure requires that the secondary member device be rebooted. This is also a false statement. Recovery from a control link failure does not require rebooting the secondary node1. The secondary node can rejoin the cluster when the control link is restored and the configuration is synchronized2.
References:
1: Configuring Chassis Clustering on SRX Series Devices
2: Chassis Cluster User Guide for SRX Series Devices
3: Connecting SRX Series Firewalls to Create a Chassis Cluster
4: RFC 1918 - Address Allocation for Private Internets
https://supportportal.juniper.net/s/article/SRX-Secondary-node-of-a-Chassis-Cluster-is-in-Disabled-state-how-do