He volunteered as an english teacher at a catholic orphanage .

他自愿去一家天主教孤儿院教英语。

I volunteered about thirty to forty hours a week during the summer .

我自愿在暑假里一个星期在那里工作30到40个小时。

Four times as many russians volunteered to act as election observers as in december .

从12月以后，许多俄罗斯人已经四次自愿承担选举观察员的身份。

She volunteered to help train search-and-rescue dogs .

她还志愿参加了帮助训练搜救犬的工作。

He then volunteered to demonstrate the validity of his opinion .

接着他又主动要求证明这一看法的正确性。