物质的性质决定物质的用途。下列物质的用途中,主要利用其化学性质的是 ①天然气主要成分甲烷用作燃料 ②氢气作高能燃料 ③氮气用做保护气 ④干冰用作制冷剂 ⑤二氧化碳用作气体肥料 ⑥木炭用于除冰箱异味 ⑦金刚石用于裁玻璃 ⑧活性炭用于防毒面具 ⑨一氧化碳工业用于炼铁 ⑩石墨用作电极材料 ⑾用炭黑制成的墨汁书写或绘制的字画能够经久不变色
Did they _________ for the music competition? Yes, they did. A. come B. came
What did you see? I ________ lions and tigers. A. see B. saw
Yesterday Sam and I went ______ a bike ride. A. for B. of
Listen and tick (听音找出相应的图片,并在括号里画√表示)10’
Are you behind the tree?______ A.Yes,I'm. B.No,I'm.C.Yes,I am.