简述下肢的浅静脉分支
参考答案：
足背静脉弓，大隐静脉-小隐静脉，
大隐静脉5条属支：股内侧浅静脉，股外侧浅静脉，旋髋浅静脉，腹壁浅静脉
Following recent reports about a ripener used in several provinces, experts said the chemical
_____ ripens fruits and vegetables does no harm to human health.[ ]
A. who
B. that
C. why
D. how
已知两个力F1与F2的大小分别为10N和30N，则它们的合力大小不可能等于（）
A．15N
B．20N
C．35N
D．40N
