题目：
____he wants to say is____ great an effort he has made to help her out.
A．That; how
B．What; what
C．What; how
D．What; that
答案：
答案：C
考查名词性从句的连接词。____he wants to say是主语从句，去从句缺少say的宾语，要用What引导，排除A；____ great an effort he has made to help her out是表语从句，且____ great an effort是感叹句作made的宾语，修饰形容词great，用how引导。所以选C。
±2SD的范围内时，其可信限的范围是（）.