连接词 + 过去分词
Dont speak until spoken to.
Pressure can be incrased when needed.
Unless repaired, the washing machine is no use.
连词 + 现在分词
Look out while crossing the street.
连词 + 形容词/其他
常见的有it necessary、if possible、when necessary、if any等
Although they are poor,they are warm-hearted.
even if或even though引导让步状语从句,表示即使,纵然,用来使人注意下文所强调内容的性质.
Ill get there even ifI have to sell my house to get enough money to go by air.
Dont trust him, no matter what / whatever he says.
Whoever breaks the law will be published.
No matter how hard the work is, youd better try to do it well.