According to the passage, which of the following is a necessity（）

单项选择题22()

A．houses
B．dogs
C．pets
D．families

单项选择题The author’s purpose in writing the passage is （）

A．to help children to gain a better understanding of animal life
B．to prove that the saying "a rolling stone gathers no moss" is wrong
C．to introduce a particular animal to the common reader
D．to discuss with professionals the laziness of animals