化简： ÷ =____．

关于能源，下列说法正确的是（　　）

    Each year thousands of____ (explore) and tourists visit the polar regions of the Arctic and Antarctica. But the increasing number of people travelling to the ends of the Earth' can have a negative effect____ fragile ecosystems. Should tourists____(allow) to visit polar regions?

    About 40,000 tourists visit Antarctica each year, More than five million travel to the Arctic and sub-Arctic. Transporting tourists to the regions ____(increase) ship and airplane traffic, adding to the risk of pollution, oil spills, and other ____(environment) damage. Because the places where wildlife is accessible ____(be) few in numbers, tourist traffic can become concentrated in specific areas,____ (put) Arctic vegetation at risk.

    Others say that access____ these very special parts of the world should not be restricted to only researches and scientist. Polar tourism allows people to develop deep personal connections with polar regions. “Those ____travel to the Arctic or Antarctica often become cheer leaders for supporting those places” Jim Sano, vice president for travel and____(conserve) at World Wildlife Fund, told TFK.

 利用如图所示装置探究“物体的动能大小与哪些因素有关”。将小球A、B分别拉到与竖直方向成一定角度θ的位置，然后都由静止释放，当小球摆动到竖直位置时，将与静止在水平面上的木块C发生碰撞，木块都会在水平面上滑行一定距离后停止。图中的摆长L都相同，θ1＜θ2，球A、B的质量分别为m_A、m_B(m_A<m_B)。

(1)如图甲、乙所示，同时释放A、B，观察到它们并排摆动且始终相对静止，同时到达竖直位置。这表明两小球在摆动过程中的任一时刻的速度大小与小球的____ 无关。
(2)如图甲、乙所示，观察到B球能将木块C撞得更远。由此可得出
结论：____。
(3)图乙中小球B到达竖直位置时的速度____ (选填“大于”、“小于”或“等于”)图丙中小球B到达竖直位置时的速度。
(4)如图乙、丙所示，丙中木块C滑行得更远些，由此可得出结论：____ 。