具有密封性能较好，泄压反应较快，泄放装置是（）。
A．安全阀
B．爆破片
C．单向阀
D．自动阀
参考答案：B
Not until I was a senior student the importance of English. [ ]
A. I have realized
B. did I realize
C. have I realized
D. I realized
个位、十位、百位、千位、万位…都是______；个、十、百、千、万…______．
