______ earthquake happened on ______ morning of April 14th in Yushu, Qinghai. By far, over 2,000 people have died.
A:A ; the
B:An ; the
C:An ; a
①写出红磷在空气中燃烧的化学反应表达式____.
②待红磷熄灭并冷却后,打开弹簧夹,观察到烧杯中的水进入集气瓶,瓶内水面最终上升约至1刻度处.由此可知氧气约占空气总体积的____.
③红磷熄灭后,集气瓶内剩下的气体主要是____,该气体____(填“支持”或“不支持”)燃烧.
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