You don’t know how difficult the job is you have done it yourself.A. unlessB. sinceC. ifD.

问题补充：

You don’t know how difficult the job is,you have done it yourself.

A. unless

B. since

C. if

D. because

答案：

(答案→)A. unless

B. since

C. if

D. because

解析：句意：你不知道这项工作有多么难，除非你亲自做了。A除非，如果不，B自从C如果D因为，根据句意故选A