it was a letter to cheer them up. 中的it起什么作用?

帮忙看看是cheer them up 还是cheer it up 请问It's time to cheer me up. it was nice to get your last letter什么意思 it was up to me it was time for them( )home A.go B.to It\'s your turn to be on duty这个句子中的动词不定式起什么作用? it was nice of them to call 帮忙看看这里which起什么作用?It led to a series of international trade n 英语翻译I ask them to take a poem and hold it up to the light li 英语翻译Cheer up!It doesn’t have to be that bad.Here are some si it was up to 的用法 It was a simple letter asking for a place to study at Scotla