My pen pal Ann found it difficult Chinese well.A. learningB. learnC. to learnD. learned

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。