Read the paragraph.
Chimpanzees are very interesting animals. They are very similar to humans in the way they act. They are also very smart. Chimpanzees learn how to use tools to get food. They use twigs to dip for insects inside of holes in trees. They also use rocks to crack open nuts. Chimpanzees _________ learn how to use these tools before they turn 8, or they will not be able to learn them and they will go hungry.
Choose the correct word to fill in the blank.
A.
can
B.
may
C.
must
D.
would