单选题
_______ hearing is really produced in all animals by the effect of pressure is not definitely known by scientists.
A、
If or not
B、
Whether or not
C、
have never heard of
D、
had never heard of
【正确答案】
B
【答案解析】
a. If or not (if后不能加not) b. Whether or not （whether 引导的主语从句）
提交答案
关闭