Question

--- What can I do for you?
--- I’d like to buy a present for my son, _______ at a proper price but of great use.

1. A.
   one
2. B.
   the one
3. C.
   which
4. D.
   that

Answer 1

A
试题分析：考查代词：分析句子结构：后半句 “at a proper price but of great use” 没有动词，不是一个完整的句子，所以不选连接词which 和 it，而one可以做代词，指代a present，the one有特指的意思，这里还没有选好礼物，不用特指。选A。
考点：考查代词辨析
点评：It指代上文出现的同一事物；that指代可数名词单数或者不可数名词，后面一定要有定语修饰；one表示泛指，指代可数名词单数。