听第三段材料，完成第16-20题
16．The little fish lives____．
A．in a bottle
B．in a river
C．in the sea
17．Which is NOT true？
A．The little fish isn't afraid of the dark．
B．The little fish has lots of friends．
C．The little fish can't play with her friends．
18．The little fish usually feels happy because____．
A．she can play with her friends
B．She can swim everywhere
 C．Both A and B
19．The little fish's mother often asks her to be careful because____．
A．the river is dark
B．some big fish may eat her
C．man may catch her
20．The little fish's family will leave their home because____．
A．the water there is getting dirtier and dirtier
B．the food there is becoming worse and worse
C．Both A and B．