湖泊生态系统在结构上可分为三个层,即浅水层、______、深水层。
参考答案:表水层
— Excuse me, may I start right now?
— ________.[ ]
A. It's none of my business
B. You have got it
C. Sure, go ahead.
D. It's your turn
6个月~6岁小儿血红蛋白正常值的低限是
A.80g/L
B.90g/L
C.100g/L
D.110g/L
E.120g/L