问题补充:
My pen pal Ann found it difficult Chinese well.
A. learning
B. learn
C. to learn
D. learned
答案:
A. learning
B. learn
(答案→)C. to learn
D. learned
解析:句意:我的笔友安发现学好英语很难。主语+find+it+形容词+to do sth (动词不定式),某人发现做某事是怎么样的,it 是形式宾语,形容词做宾补,不定式是真宾语。结合语境可知选C。