上、下止点，活塞的运动方向将得到改变，活塞的速度等于（）。
参考答案：零
I really appreciate ____ to relax with you on this magicisland. [ ]
A. having time
B. to have time
C. to have had time
D. to having time
血浆胶体渗透压降低可引起的变化有（）
A.血容量增多
B.有效滤过压增高
C.细胞内液减少
D.组织液容量增多
E.进入毛细血管的水分减少
