问题补充:
What seems to be a simple idea always turns out that is hard to put into practice.
A. the one
B. one
C. ones
D. another
答案:
A. the one
(答案→)B. one
C. ones
D. another
解析:句意:看似简单的想法结果总是成为一个很难实施的想法。这里需要代词代替an idea,用one可以泛指可数名词的单数,the one是特指可数名词单数,ones是泛指可数名词复数,another“另一个”,所以选B。