A. I'm number thirteen.
B. He's a postman.
C. He is in Class Two.
D. I'm number three, too
________ tourists like to climb the Great Wall, and ________ them is increasing now.
Even the extreme climate can’t prevent polar bears wander on the beach.____
人体的每个肾脏是由约100万个肾单位组成的,如图为一个肾单位的结构示意图.以下有关叙述中正确的是( )