太平天国运动最重要的纲领性文件是：（）。
A.《太平条规》
B.《资政新篇》
C.《天款十条》
D.《天朝田亩制度》
参考答案：D
用斜面和滑块做“测物体的平均速度”实验，当滑块自顶端出发时开始计时，滑至斜面底端时停止计时，如图所示。在此过程中，滑块的平均速度是（ ）
A．10cm/s
B．9cm/s
C．8cm/s
D．7cm/s
Which statement is TRUE concerning the danger signal?（）.
A.When any vessel fails to understand the intentions of an approaching vessel she must sound the danger signal
B.Only the stand-on vessel can sound the danger signal
C.Distress signals may be used in place of the danger signal
D.The danger signal consists of 4 or more short blasts of the whistle
