赤芍具有的功效是()
A.清热凉血,活血散瘀
B.清热凉血,祛瘀止痛
C.凉血活血,解毒透疹
D.凉血止血,泻火解毒
E.凉血退蒸,清泻肺热
参考答案:B
The new technology has opened up a very wide ______ of possibilities. [ ]
A. range
B. extent
C. number
D. collection
如图所示,两平行光滑导轨相距0.2m,与水平面夹角为300,金属棒MN的质量为0.2kg,金属棒的电阻R=1Ω,其处在与轨道平面垂直且磁感应强度为5T的匀强磁场中,电源电动势为5V,内阻为1Ω,为使MN处于静止状态,则电阻R1应为多少?(其他电阻不计)