【1】本句是成语。when连词，当…时候； in Rome在罗马, do动词，做； as 连词，依照；the Romans罗马人。所以答案为：When in Rome, do as the Romans do.。

【2】根据句意可使用含有情态动词的被动句，should be+动词过去分词。take action采取行动；more action(s)更多的行动；should 情态动词，应该；be taken 被动结构； protect the environment保护环境。所以答案为：More action(s) should be taken to protect the environment。

【3】宁愿…而不愿，可以表示为“would rather do…instead of…/prefer…to(介词)…/would rather…than do sth.”he人称代词，他；would rather宁愿，后跟动词原形；walk home步行回家； instead of 代替，后跟名词/代词/动名词。spend…doing…花费…做某事；much money很多钱； taking a taxi.乘坐出租车。所以答案为：He would rather walk home instead of spending much money taking a taxi./ He preferred walking home to spending much money taking a taxi./He would rather walk home than spend much money taking a taxi.  

【4】根据语义可知，本句为can 开头的一般疑问句。you 你，在句中作主语；imagine动词，想像；what life will be like in the 22nd century在句中作宾语，使用陈述句的语序。in the 22nd century在22世纪。所以答案为：Can you imagine what life will be like in the 22nd century?

【5】as 连词，随着；time名词，时间； goes动词三单，go by时间流逝；主句使用现在进行时态的句子。China 名词，中国；be becoming/getting richer and stronger. 变得越来越富强。所以答案为：As time goes by. China is becoming/getting richer and stronger.。