下肢深静脉血栓脱落最容易栓塞的部位是（）
A.肾
B.肺
C.脑
D.心
E.肝
参考答案：B
— Does your brother serve in the army?
— No, not now. But he _______ in the army for 8 years.[ ]
A. would serve
B. served
C. had served
D. was serving
群落演替系列达到最后稳定阶段形成的稳定群落即为顶极群落。 ( )
