Tom has two _____________. [ ]
A. box
B. pen
C. computers
D. car
答案:C
如图12-3-11所示中的实线是一列简谐横波在某一时刻的波形图线,经0.3 s后,其波形如图中虚线所示.设该波的周期T大于0.3 s,求:
图12-3-11
(1)波长和振幅;
(2)若波向右传播,求波的周期和波速;
(3)若波向左传播,求波的周期和波速.
胁痛的常见病因有下列哪几项
A.情志不遂
B.跌仆损伤
C.饮食所伤
D.劳欲久病
E.外感湿热