练习：

3.The little boy is very ambitious; he's filled with ____ for knowledge.

a. aspiration
b. inspiration
c. respiration
d. expiration

4. I can't remember anything; my memory is like a ____ .

a. filter
b. net
c. sieve
d. web

答案及讲解：

3. a

aspiration
n.
热望, 渴望

inspiration
n.
灵感

respiration
n.
呼吸, 呼吸作用

expiration
n.
终止；截止 （亦作： expiry）

4. c

filter
n.
滤波器, 过滤器, 滤光器, 筛选

net
n.
网, 网络, 网状物

sieve
n.
筛, 滤网

web
n.
网, 蛛丝, 蹼, 翼手, 织物, 圈套