当注入气体中氧气的体积分数为5％时，燃烧气硫化氢的体积分数大于或等于（）就达到了起爆极限。
A、2．5％
B、5％
C、7．5％
D、lO％
参考答案：C
第十五届哈洽会开幕当天，牡丹江市代表团引进资金约为2 200 000 000元，用科学记数法表示为______元．
--- Could you tell me ?
--- His home is quite far away from the office, I think.
A．whenhegotup
B．whyheboughtthecar
C．whereheworks
D．howhelikeshisjob
