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【单选题】
冠桥焊接前一般用石膏和石英砂的比例是多少，再混合加水调拌后包埋( )
A.
1︰1
B.
1︰2
C.
1︰3
D.
1︰4
E.
1︰5
参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】对于洪峰或洪量频率（）的洪水以及对电网、水电厂运行造成重大影响的洪水，有关网、省调要认真总结洪水调度情况，并在洪峰发生后的7日内将文字分析材料以电子邮件方式上报国调及上级网调。
A.
小于等于5%
B.
小于等于10%
C.
小于等于15%
D.
小于等于25%
【单选题】When stars like our Sun die, they bloat to become red giants and then eject gigantic clouds of gas and dust into space. Increasingly, however, scientists found themselves at a profound loss to explain...
A.
explain-the possible way of death of our Sun.
B.
show the two types of red giants.
C.
discuss on the way of red giants to become white dwarfs.
D.
explore the origin of life.