防护区应设置泄压口,并宜在外墙上,其高度不应大于防护区净高的2/3。当防护区设有防瀑泄压孔时,可不单独设置泄压口。()
参考答案:错
How many________ do you need to finish this article?
A.paper
B.papers
C.piece of papers
D.pieces of paper
鉴别Na2CO3与NaHCO3两种固体,最好的方法是
A.加热
B.加水
C.加NaOH溶液
D.加Ca(OH)2溶液