从以上单词中选出最适当的一个单词,填入空格内.
1 We found a(n) ( ) of elephants running together.
2 We buried the dead cat in a little ( ) dug in the backyard.
3 Some people learn by ( ) and others by experience.
4 A(n) ( ) worker deserves good pay.
5 ( ) are usually used to irrigate field and carry off water.
答案：
1 We found a(n) (herd) of elephants running together.
2 We buried the dead cat in a little (grave) dug in the backyard.
3 Some people learn by (experiment) and others by experience.
4 A(n) (efficient) worker deserves good pay.
5 (Ditches) are usually used to irrigate field and carry off water.
