It was his parents' help________ enabled him to buy an apartment in the big city.
考查强调句。去掉It was 后的剩余部分仍然时隔完整句子，由此判断是强调句；his parents' help表示的不是人， 故用that。 翻译:在父母的帮助下他才能在大城市里买了房。