There        a lot of manatees, but now there aren’t very many of them．

A． used to have                 B． used to be  

C． are used to be               D． used being

根据图画及上下文提示，在下面对话的空白处填入适当的话语（话语可以是句子、短语或词），使对话完整。

A: Hey, Ginny．What do you call those big, gray things in the water?

B:  1           ．

A: What?

B: Manatees．They’re very gentle and very shy．

A:  2            ?

B: They’re usually about 10 feet long and they weigh about 1,000 pounds．

A: How much do they eat everyday?

B: They need about 100 pounds of aquatic food a day．

A:  3            ?

B: It is underwater plants and vegetation （植被)．

A: That’s what they eat?

B: Yes, it is．

A:  4           ?  

B: Yes, they are endangered．But, we’re trying to save them．

A: Wait a moment．Why are they endangered?

B:  5            ．

A: Where do they live?

B: They live in the swamps（沼泽）．6            ．They are endangered also because there sometimes isn’t enough food for all of them．

A:  7           ．There used to be a lot of manatees, but now there aren’t very many of them left, I think．

B: Yes,  8           ．At this point, there are only about 2, 500 in the U．S．

A:  9            ?

B: Since 1927 laws have been passed to protect them．

A: Thank you for your information．

B:  10           ．