质量为200g的子弹在枪膛中受到火药的推力为500N，不考虑空气阻力，画出子弹在空中飞行时受到的力的图示。
-How do you usually go to work, Miss Green?
--I usually go to work ___ foot, but sometimes __ my bike.
A．on, by
B．on, on
C．by, on
D．by, by
小腿青筋的临床意义是（）
A.热盛血瘀
B.寒湿内侵，络脉血瘀
C.心肾阳衰
D.风湿郁久化热
E.先天不足，肾气不充
