In the USA he made a lot of friends English well to make himself .A. learn; understand

问题补充：

In the USA, he made a lot of friends English well to make himself .

A. learn; understand

B. to learn; understood

C. learning; understand

D. learned; understood

答案：

A. learn; understand

(答案→)B. to learn; understood

C. learning; understand

D. learned; understood

解析：第一个空是不定式作目的状语；第二个空是过去分词作宾补。