客梯的轿厢面积超过标准规定时，应如何处理？
参考答案：
应按实际面积在GB7588表2中查出相应的起重量，按该额定起重量设计、制造和验收。
—He looks unhappy.
—Yes, but he can't say what it is ______ is bothering him.[ ]
A. as
B. that
C. what
D. which
