表語從句啊It is+表語（所謂的主+系+表） 表語用as if引導(dǎo),翻譯出來就是：
好像是一件無關(guān)緊要的小事引起了一連串的連鎖反應(yīng)
舉幾個(gè)例子吧
She looks as if she were ten years younger．
她看起來好像年輕了十歲.
It seems as if our team is going to win．
看來我們隊(duì)要?jiǎng)倭?
It looks as if a tornado swept through your room.
好像有龍卷風(fēng)席卷過你的房間.
It looks as if they're looking for something.
他們看起來好像在找什么東西.