1.B
2.C [the bats have had some 50 million years of evolution to refine their sonar]
3.D [ on examining their stomachs‘ contents,Spallanzani found that they had been able to capture and fill themselves with flying insects]
4.A [ Their physiological mechanisms for echo location...]
5.A [...even when the insects emit no sound that can be heard by human ears...It will even detect and chase pebbles tossed into the air.]