B. 'Bats have some fascinating characteristics. For one thing, they are the only mammals that truly fly. Furthermore, they are the only animals that roost hanging upside down. Insect-eating bats have an astonishing hearing. "Some can hear individual insects walk or flutter their wings. Most insect-eating bats use echolocation to catch insects at night: the bats emit squeaks (too high-pitched for us to hear that bounce off insects and surrounding objects and echo back, enabling them to follow a moth's zigzag flight or distinguish, say, a mosquito from a gnat. "Bats are so adept at locating insects that a single bat may eat several thousand within one night 3. The main pattern of organization of the selection is? ​