题目

下列植物中，最低等的是（  ）A.藻类植物 B.苔藓植物 C.蕨类植物 D.被子植物 答案：A— Hi, Tom．Any idea where Mary is? — She    in the reading room．I saw her there just now．A．shall beB．should have beenC．should beD．might have been