问题补充:
TV set is one of in the world.
A. most useful invention
B. the most helpful inventions
C. more helpful inventions
D. less useful invention
答案:
A. most useful invention
(答案→)B. the most helpful inventions
C. more helpful inventions
D. less useful invention
解析:句意:电视机是世界上最有用的发明之一。这里one of+可数名词的复数,故排除AD;这里用了最高级所以它的前面应该用定冠词修饰。故选B。