托福阅读真题+题目+答案：Hermit Crabs in Scall Shell

托福阅读真题+题目+答案：Hermit Crabs in Scall Shell

Hermit crabs depend on a properly fitting snail shell for protection from predators. Crabs in shells that are too small grow more slowly, are less tolerant of air exposure and drying out, and are more likely to be eaten by a predator than those that can withdraw completely into their shell. When a crab has outgrown its snail shell, it has to look for a bigger one that fits properly. They locate shells by smell, either when the preceding owner (the snail) dies and begins to decay or by detecting calcium, the major component of snail shells. The crabs do not generally kill snails to find new shells, although they may fight with other hermit crabs over empty shells, especially when empty shells are scarce. After locating a new shell, the crab investigates its surface and internal size by rolling it over and exploring it with its claws and walking legs. If it looks like a good fit, the crab withdraws its abdomen from its old shell and inserts it into the new one so quickly that it can be difficult to see. Switching shells is risky-the crab could be attacked by a predator or lose one or both shells to other hermit crabs.

1, The word "preceding" in the passage is closest in meaning to

A, sick

B, earlier

C, similarly sized

D, natural

2, Why does the author point out that "Switching shells is risky" for hermit crabs?

A, To suggest that hermit crabs rarely switch shells

B, To illustrate the consequences of moving into a poorly fitting shell

C, To provide an explanation for why many hermit crabs remain in a shell that is too small for them

D, To explain why hermit crabs insert themselves into their new shell very quickly

3, According to paragraph 1, all of the following are disadvantages a hermit crab may experience when occupying a shell that is too small EXCEРT:

A, The crab is more likely to suffer from drying out.

B, Predators can reach the crab more easily.

C, The crab has less access to fresh air.

D, The crab grows more slowly.

4, According to paragraph 1, what is the first thing a hermit crab does after locating a new shell?

A, Force the current owner out of the shell

B, Insert its abdomen into the shell quickly

C, Determine whether the shell is the right size

D, Roll over to make switching shells easier

Particular species of hermits tend to prefer certain species of snail shells, but size is the critical factor. Occupying larger and heavier shells gives them greater protection, but it takes more energy to lug a large house around. Shells often become covered with other organisms, such as barnacles or algae, that make them heavier and more difficult to carry. Some hermit species live in shells that get entirely covered by bryozoan colonies that eventually dissolve the snail shell, leaving the crab with a house composed entirely of the bryozoans. As the bryozoan colony grows, so too do the crabs, so these crabs have no need to change their homes.

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