职称英语考试

【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

网考网参考答案：B
网考网解析：
a. If or not (if后不能加not) b. Whether or not （whether 引导的主语从句） 查看试题解析出处>>