Question

read the passage
roach robots to the rescue
when buildings collapse, it is extremely difficult to safely locate and rescue people trapped inside. victims may be wedged into small spaces, and unstable rubble could collapse on rescue workers. an alternative to human rescue workers may be robotic cockroaches. real cockroaches are protected by strong yet flexible exoskeletons. they can also flatten their bodies through tiny cracks. a robotics researcher from harvard university and a biomechanics expert from the university of california, berkeley, were inspired to create mini robots that have the same features. the roach robots can squeeze through small spaces and skitter over unstable environments. fitted with cameras and microphones, they could be used in disasters to locate victims.
what is the main, or central, idea of the passage?
it is dangerous to search inside collapsed buildings, but cockroach - like robots can go places where human searchers cant or shouldnt.
inspired by the strength and quickness of cockroaches, researchers created robots with the same characteristics.
cockroach - like robots can fit through small cracks and move through unstable rubble.

Explanation:

The passage first points out the danger of searching in collapsed buildings for human rescuers. Then it introduces cockroach - like robots that can access places human searchers can't due to their unique features. The other two options focus only on parts of the information, not the overall main idea.

Answer:

It is dangerous to search inside collapsed buildings, but cockroach - like robots can go places where human searchers can't or shouldn't.