Study sentences a-f in the texts and tick the best choice.
1) These sentences sound better in the passive than in the active because we are more interested in the … (1)
　 a. actions 　 b. people 　 c. time
2) Which auxiliary verb do we use in every sentence (2)
　 a. have 　 b. be 　 c. do
3) Every passive sentence has a(n) … (3)
　 a. infinitive(不定式) 　 b. -ing form 　 c. past participle（过去分词）
4) To mention the person or thing that does the action we use the word … (4)
　 a. because 　 b. by 　 c. for__4__(完形填空)
.a
.b
.c