We may find that learning a foreign language does not have to be________learning our mother tongue，but can in fact be twice ________.

Mr. Bryan is a/an _______ secretary in our office, for he is able to do tasks successfully, without wasting time or energy.

This argument sounds reasonable, but ___________ it’s incorrect. 

We are taught that business letters should be written in a formal style           in a personal one.

These　good　sare＿＿for　export，though　a　few　of　them　may　be　sold　on　the　home　market．