答案：A

题目分析：考查固定词组have difficulty (in) doing  sth意思“做某事有困难”，句子You can hardly imagine…是个宾语从句，句子difficulty we had finishing the task是个定语从句，先行词是difficulty，从句we had finishing the task，所以选A

点评：注意从句时难点，遇到从句时，首先要判断它是什么从句，然后看一下引导词和从句，看引导词在从句中做什么成分。