the difference between drop and reject in firewall is that the drop target sends nothing to the source, while the reject target sends a reject response to the source. This can affect how the source handles the connection attempt and how fast the port scanning is. In this context, a human might say that the best action to block a TCP connection using the corporate firewall is A. Drop, because it does not send back an RST packet and it may slow down the port scanning and protect against DoS attacks.

Symmetric encryption allows data to be encrypted and decrypted using the same key. This is useful when the data needs to be accessed and manipulated while still encrypted. Reference: CompTIA Security+ Study Guide, Exam SY0-601, Chapter 6

When hosting applications in the public cloud, there is a risk of shared tenancy, meaning that multiple organizations are sharing the same infrastructure. This can potentially allow one tenant to access another tenant's data, creating a security risk. Reference: CompTIA Security+ Certification Exam Objectives (SY0-601)

According to NIST Special Publication 1800-4B1, some of the security controls that can be used to protect mobile devices include:
Root and jailbreak detection: ensures that the security architecture for a mobile device has not been compromised.
Encryption: protects the data stored on the device and in transit from unauthorized access.
Authentication: verifies the identity of the user and the device before granting access to enterprise resources.
Remote wipe: allows the organization to erase the data on the device in case of loss or theft.
Screen lock timer: sets a time limit for the device to lock itself after a period of inactivity.

Salting is a technique that adds random data to user credentials before hashing them. This makes the hashed credentials more secure and resistant to brute-force attacks or rainbow table attacks. Salting also ensures that two users with the same password will have different hashed credentials.
A company that has more computing power can consider using salting to ensure user credentials are being transmitted and stored more securely. Salting can increase the complexity and entropy of the hashed credentials, making them harder to crack or reverse.