I think Father would like to know I've been up to so far, so I decide to send him a quick note
A. which
B. why
C. what
D. How
网友回答
A. which
B. why
(答案→)C. what
D. How
解析：主要测试宾语从句。由句子语境可知：动词know需要宾语从句，同时句子I've been up to so far中缺少介词to宾语，答案中能够充当双重成分的引导词只有what。