I don't think you will have any difficulty _____his English speech A.to understand. B.in unders...I don't think you will have any difficulty _____his English speechA.to understand. B.in understanding答案是B,为什么A不行?A也说的通啊

I don't think you will have any difficulty _____his English speech A.to understand. B.in unders...I don't think you will have any difficulty _____his English speechA.to understand. B.in understanding答案是B,为什么A不行?A也说的通啊
I don't think you will have any difficulty _____his English speech A.to understand. B.in unders...
I don't think you will have any difficulty _____his English speech
A.to understand. B.in understanding
答案是B,为什么A不行?A也说的通啊

I don't think you will have any difficulty _____his English speech A.to understand. B.in unders...I don't think you will have any difficulty _____his English speechA.to understand. B.in understanding答案是B,为什么A不行?A也说的通啊
因为 difficulty in sth 是固定句型
difficulty in understanding 在理解方面的困难

have some difficulty in doing sth是固定搭配