单项选择题

According to the passage, why is the shape of sea cucumbers important

A．It helps them to digest their food.
B．It helps them to protect themselves from danger.
C．It makes it easier for them to move through the mud.
D．It makes them attractive to fish.

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单项选择题

Which of the following would NOT cause a sea cucumber to release its internal organs into the water

A．touch.
B．Food.
C．Unusually warm water.
D．Pollution.

单项选择题

The fourth paragraph of the passage primarily discusses ______.

A．the reproduction of sea cucumbers
B．the food sources of sea cucumbers
C．the eating habits of sea cucumbers
D．threats to sea cucumbers' existence