When + V-ing …

结构︰

when/while/once/if/unless/though+现在分词

说明︰

当when,while,once,if,unless,though 等<副词><连接词>引导<副词子句>时,若其<主语>与<主要子句>相同,可保留该<副词><连接词>,其余部分则化简为<分词词组>。

He says “Please” when making a request.
请求时,他说:“请”。
When waiting for a bus, he takes his turn.
等公共汽车时,他按顺序排队。
He stopped to talk to me when seeing me.
看到我的时候,他停下来和我说话。
If falling I’ll, I’ll stay home taking a good rest.
如果生病,我会待在家里好好休息。
Once arriving there, I’ll keep contact with you.
一到那里,我会跟你连络。
Unless (being) rich, I am not going to buy a house.
除非有钱,要不然我是不会买房子的。
Though knowing the truth, he remained silent.
虽然他知道实情,却保持沉默。