生态系统中的能量是通过 依次传递的。食物链上的每一个环节,叫做一个 。
食物链;营养级
This pen doesn't look like ______. ______pen has been lent to Xiao Wang. I think it must be______.
A.me; My; her
B.my; Mine; hers
C.mine; My; her
D.mine; My; hers
原发性免疫缺陷病患儿最常见的感染部位是()
A.皮肤感染
B.呼吸道感染
C.胃肠道感染
D.败血症
E.脑膜炎