题目内容：

    Being able to land safely is a critically important skill for all flying animals. Whereas terrestrial animals face no particular challenge when they need to stop running or crawling, flying animals move at much higher speeds, and they must be careful about how they land. Hitting the ground, or even water, at full flight speed would be quite dangerous. Before touching down, they must decrease their speed in order to land safely. Both bats and birds have mastered the skill of landing, but these two types of flyers go about it quite differently.

In the past it was believed that, in terms of flying mechanics, there was little difference between bats and birds. This belief was based only on assumption, however, because for years nobody had actually studied in detail how bats move their wings. In recent years, though, researchers have discovered a number of interesting facts about bat flight. Bats are built differently from birds, and their wings incorporate(结合) both their front and hind limbs (后肢). This makes their limbs working together more difficult for bats and, as a result, they are not very good at flying over longer distances. However, a bat can quickly change its direction of flight or completely reverse it, something a bird cannot easily do.

Another interesting characteristic of bat flight is the way in which bats land—upside down! Unlike birds, which touch down on the ground or on tree branches, bats can be observed flying around and then suddenly hanging upside down from an object overhead. How do they do it? A group of researchers recently used video cameras to film bats landing on nets suspended from the ceiling of their laboratory and studied the recordings in slow motion. They painted spots on the bats’ wings to see in detail what happens to the wings in flight and during touchdown. It turns out that the bats flew in a straight line up to the net and then quickly flipped over and attached themselves to it upside down. One disadvantage to this landing routine is that the bats often slam into their landing spot with some force, which probably causes pain. However, not all bats hit their landing spots with the same speed and force; these will vary depending on the area where a bat species makes its home. For example, a cave bat, which regularly rests on a hard stone ceiling, is more careful about its landing preparation than a bat more accustomed to landing in leafy treetops.

1.In line 1, the word terrestrial is closest in meaning to _______.

A. high-flying B. fast-moving C. tree-climbing D. ground-living

2.According to the passage, what skill is crucial for flying animals?

A. Diving underwater.

B. Slowing down to land.

C. Flying over great distances.

D. Balancing on high branches.

3.According to the passage, what is an advantage that bats have over birds?

A. Bats can land on a greater variety of surfaces.

B. Bats can turn in the air more quickly.

C. Bats can eat while flying.

D. Bats are lighter.

4.What is the main topic of the passage?

A. Places where flying animals choose to land.

B. Why scientists have difficulty observing bats.

C. Differences in the eating habits of bats and birds.

D. Ways in which bats move differently from birds.