Complete each of the following sentences with a (compound) word derived from the one(s) given in brackets.
The cause of their inharmonious （ ）lay in their lack of mutual trust. (marry)
【正确答案】：MARRIAGE
【题目解析】：
根据前文their inharmonious（他们不和谐的······）和后文lay in（在于······）可知空格处应填marry的名词形式marriage，婚姻。
句意：他们婚姻不和谐的原因在于他们缺乏相互信任。