单选题 No one could come up with an easy solution to the government's predicament—labor ______ which is caused by the wars.
[A] decline [B] vacancy [C] rarity [D] shortage

【正确答案】 D
【答案解析】shortage短缺；decline衰退；vacancy空白，空虚，空缺；rarity稀有，杰出，珍贵。句意：战争导致劳动力匮乏，没有人能就政府的这一困境提出一个简单易行的方案。