单选题 —My baby has a heart trouble. —Did the doctor find it difficult______.
【正确答案】 D
【答案解析】[解题指要] it指前一句中heart trouble。“发现做某事很困难/容易”可用find it easy/hard/ difficult to do表示。如:We find it hard to learn.因而D选项不定式to treat符合题意。