Which of the following is an adaptation that allows bats to fly?

Many mammals run and walk. Some hop, swim, and even glide from trees. But only one group of mammals can truly fly: bats! Bats live in a variety of habitats around the world, from deserts to mountaintops. The short-nosed fruit bat lives in tropical forests. These bats are only active at night. They fly fast and low, sometimes covering 62 miles (100 km) in one night in search of fruit. During the day, they roost in caves and palm trees.
Which of the following is an adaptation that allows bats to fly?
feathers
long finger bones
hollow bones
A bat's bendable wings are supported by arm bones and long, flexible finger bones. The wings stretch from the tips of their fingers down to their feet. They're made from two layers of skin that extend from the back and belly.
Most bats hunt at night. A bat can find its way and locate food in total darkness using:
excellent eyesight
its highly-sensitive nose
high-pitched sounds
Although they also have good eyesight, most bats can send out high-pitched squeaks from their throats. Then they listen for the echoes to sense objects in their environment. They do this to navigate through forests and caves, detect food, and track tiny insects. This ability is called echolocation.
Scientists think that the ancestor of flying bats was:
a flightless mammal
another flying mammal
birds
They think bats evolved more than 50 million years ago from a mammal with four limbs--but no wings. Unlike the long fingers of bats, this non-flying ancestor probably had short fingers. Changes in a single gene may have been largely responsible for this shift from short to long fingers.
Nearly one fifth of all living species of mammals are bats.
There are about 5,400 known living species of mammals. More than 1,000 of these are bats!
Some bats can make a sharp u-turn while flying.
Some bats are very acrobatic flyers! One reason is that when bats fly, their wings bend to create spiraling air currents. These currents under their wings give them greater mobility.
The short-nosed fruit bat has sharp, pointy teeth.
Sharp teeth are more common in bats that eat insects. Fruit-eating bats usually have wider, rounded teeth, more like humans.
Scientific Name: Cynopterus sphinx
Habitat: tropical forests in South Asia
Diet: flowers and fruits (figs, guavas, mangoes)
Size: body and head less than 6 inches (15 cm) long; average wingspan about 15 inches (38 cm)
Conservation Status: least concern
Cool Fact: They're also called dog-faced bats.
Cool Fact: Like many bats, they hang head-down from their clawed feet when resting or roosting.