美国正在实验助推火箭无损回收技术：火箭将飞船推送至一定高度；箭船分离，火箭停止喷火、落向地面；接近地面时，火箭再次消耗燃料、向下喷火，并以2m/s的速度匀速下降，如图所示．匀速下降时，火箭的动能 ____（变小/不变/变大），重力势能 ____ （变小/不变/变大）

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    The meanings of colors play an important ____in our world. What a color pass to a person of the west, may be very ____to someone in the east. While a bride(新娘) may wear white to her wedding (婚礼) in Europe or America, a bride ____China may choose to wear a traditional red dress.

Here are some ____and what they represent (代表，象征) to various people of the world.

    RED

    In China red is a ____of luck and is used for many celebrations such as wedding and at the beginning of the New Year. In the United States red represents love and is used during Christmas and so on. Red is also represents ____and power in the west.

    BLUE

    People around the world think____and the sky with the color blue. For this reason, blue is widely ____with peace and calm. But to the Cherokees (切罗基族人), blue meant trouble or failure. In the United States we have come to connect the color blue with sadness.

    GREEN

    In Paris, all garage collectors are clothed in green, drive green trucks and the bins are also green. In many parts of the world,____ has become a symbol of kindness and the earth.

    YELLOW

    Yellow is a color that symbolizes the sun. In the United States, school buses and taxis are often yellow____they can catch the eyes. But to the Egyptians, yellow was a color of mourning (哀悼).

（1）某建筑材料，主要成分为铝硅酸盐，化学式是MgAl₂H₄Si₄O₁₄；化学式改写成氧化物形式为　 ____　．该材料与酸或碱反应时可以看作各氧化物分别与酸、碱反应，则材料该与足量的氢氧化钠反应后过滤，滤渣主要是　 ____　．

（2）除去FeCl₂溶液中少量的FeCl₃最好加入　 ____　物质．

（3）鉴别Na₂CO₃和NaHCO₃溶液可选用　 ____　（填序号）．

①NaOH   ②Ca（OH）₂   ③BaCl₂   ④K₂SO₄ ⑤Ca（NO₃）₂

（4）某溶液中有①SO₄^2﹣②Mg²⁺③Fe²⁺④Al³⁺四种离子，若向其中加入过量的氢氧化钠溶液，加热并搅拌，再加入过量盐酸，溶液中大量减少的阳离子是 ____　．

（5）将盛有18mL NO₂和O₂的混合气体的量筒倒立于水槽中，充分反应后，还剩余2mL无色气体，则原混合气体中O₂的体积是 ____　．

①1.2mL        ②2.4mL        ③3.6mL        ④5.2mL

A．①②B．①③C．②④D．①④