How did Congress respond to the threat of terrorism after 9/11?A) by strengthening protections on civil liberties // B) by passing the USA...

In my mind, I think that B is the most logical answer. 
The passage of the Patriot Act after the attacks of 9.11 represents a Congressional
response to the threat of terrorism.  The issue of anthrax and other biological threats
were not something that Congress responded to as much as different branches of the
executive branch.  The climate of fear and insecurity that gripped the nation also
gripped Congress and the paradigm that was evident in much of the country was that some
sacrifice of civil liberties was needed in order to preserve security. Few, if any, were
arguing at the time that the two are not incompatible with one another.  This would make
option A not viable.  Finally, the declaration of war on Iraq did not happen immediately
after the attacks on September 11, and the link between the war in Iraq and the attacks
of that fateful day is still under severe questioning and scrutiny.  This makes the
second option the best of the four.