Question

【题目】I want to know how long ______ .

A. has he been back B. has he come back

C. he has been back D. he has come back

Answer 1

【答案】C

【解析】

句意：我想知道他回来多久了。根据句意可知，本句为宾语从句，应使用陈述句的语序，所以排除选项A.B。How long询问一段时间，其谓语应是延续性的。be back表状态，可以延续；come非延续性动词。故选：C。