Identify the attack which forces an unsuspecting user's browser to send malicious requests they did not intend.

The answer is Cross Site Request Forgery (CSRF.
This is the attack which forces an unsuspecting user's browser to send malicious requests they did not intend.  The victim use holds an active session with a trusted site and at the same time, visits a malicious site, which injects an HTTP request for the trusted site into the victim user's session, weakening its integrity.

The answer should be b.