— Do you think we’ll get somewhere in he future.— I believe it’s quite_____ that we’ll make a difference so long as we work harder.

——It will be terrible to see the nuclear war happen. ——That’s right. Nuclear science should be developed to benefit the people   _____   harm them.

One advantage of eating a balanced breakfast is ______ it can keep you energetic throughout the day. 

— I think it’s beneficial to build a library near our dormitory building.—  　　　. It will be a great convenience.

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