问题
选择题
One of the most important problems they had to consider was________of public health.
A．what
B．this
C．that
D．which
答案
答案：C
C [句意：他们必须考虑的最重要的问题之一是大众健康。句中缺少表语，且指代上文one of the most important problems，所以应用that。what和which不能用作替代词，而this作代词时指代下文。]