Question

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.
cockroach - like robots can fit through small cracks and move through unstable rubble.
inspired by the strength and quickness of cockroaches, researchers created robots with the same characteristics.

Explanation:

The passage first describes the difficulty and danger of rescuing people in collapsed buildings, then introduces roach robots inspired by real cockroaches' features, and emphasizes their ability to access areas human rescuers can't or shouldn't. The first option captures the main idea by connecting the danger of human rescue and the robots' capability to go to those places. The second option only focuses on the robots' movement ability, and the third focuses on the creation inspiration, both missing the context of rescue in collapsed buildings.

Answer:

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