When shunning, why should the shun length be kept short?

A.
To eliminate blocking traffic from an invalid address that as spoofed previously.

B.
To eliminate blocking traffic from a valid address that was spoofed previously.

C.
To prevent unwanted traffic from being routed.

D.
To prevent TCP resets from occurring.

Explanation:
This setup will block the user long enough to allow the administrator to decide
what permanent action (if any) he/she wants to take against that IP address.
REF;Safe white papers; 8
SAFE: Extending the Security Blueprint to Small, Midsize, and Remote-User Networks