⑴I'm hungry.____                       A. She's running.

⑵What are you doing?____       B. He's making noodles.

⑶What are they doing?____      C. I'm hungry, too.

⑷What is she doing?____          D. They are rowing a boat.

⑸What is Sam doing?____         E. I'm reading a book.

-- Have you finished your work         ?

-- Yes, I have. I've          finished it.

含羞草对刺激做出反应与下列哪一生理现象相同（    ）

如果一个四边形的面积正好等于它的两条对角线乘积的一半，那么这个四边形一定是（     ）