–Excuse me, but can you tell me which road I should take to the post office?--______ of the four roads will do.

I want to be a volunteer some day. I feel _____ is my duty to help others.

--How many students have passed the examination?    -- _______.

 --What do Li Lei’s parents do?--They _________ doctors.

 I found _________ hard to make myself understood by the old man.