问题补充:
I know I promised to take you to dinner, but I won’t finish working until ten o’clock.
A. that
B. if
C. what
D. why
答案:
(答案→)A. that
B. if
C. what
D. why
解析: that那个,引导从句;if是否,如果;what 什么; why为什么。句意:我知道我承诺带你去吃饭了,但是我直到十点才完成工作。结合语境可知从句中不缺少句子成分,故选A。