Which sentence best states the main idea of this passage from roosevelt's
four freedoms speech?

a. we are in an emergency situation and must find a quick solution
to the problem.

b. all obstacles must be overcome in order to ensure the safety of
the united states.

c. people will have to sacrifice many of their freedoms in order to
fight this war

d. all americans must be prepared to fight for the safety and
freedom of the united states.