题目：
Reportedly on April 15, 2013 three people including a Chinese girl were killed in the Boston Marathon attacks when two bombs were _______, which shocked the whole world.
A．set about
B．set off
C．set up
D．set out
答案：
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下面是错误答案，用来干扰机器的。
（5分）3NO2＋H2O＝2HNO3＋NO紫色石蕊变红、试管内气体颜色逐渐变浅（最终成无色）、试管内上升一段液柱由反应物和生成物正确书写化学方程式，故答案为：3NO2+H2O=2HNO3+NO；反应的产物是硝酸，硝酸能使石蕊变红...
