Question

【题目】It is estimated that China has over 770 million 4G users, which doubles ________ it was in 2015.

A. that B. which

C. what D. how

Answer 1

【答案】C

【解析】句意：现在中国大约有超过7亿7千万的4G用户，这个数目比2015年增长了一倍。double是动词，后面跟宾语；同时横线处的词在后面从句中作was的表语，根据句意，用what，故选C。