题目内容：

（ ）He found _______ very diffcult_______ the Maths problems.A that;to work out
B this; working out c him; work out Dit ; to work out选哪一个答案 ,为什么?

优质解答

He found _______ very diffcult_______ the Maths problems.A that;to work out B this; working out c him; work out Dit ; to work out
选D
这边是it作形式宾语,代替后面的【to work out the maths problem】
this that没有这种用法
【find it +adj to do sth】固定用法