【例1】 She says that she'll have to close the shop________business improves.
【解析】 unless 引导条件状语从句，意为“除非，如果不”。句意：她说如果生意不改善她将关闭商店。
【答案】 unless
【例2】 He is so busy. He cannot afford enough time with his son ________if he wants to.
【解析】 even if “即使”，引导让步状语从句。句意：他如此忙。即使他想与儿子在一起他也抽不出时间。
【答案】 even
【例3】 You can borrow my car______you promise not to drive too fast.
【解析】 as long as只要，用来引导条件状语从句。
【答案】 as long as
【例4】 It is hard for the Greek government to get over the present difficulties________it gets more financial support from the European Union.
【解析】 unless引导条件状语从句，意为“如果不”。
【答案】 unless
