管道采用石油沥青涂料外防腐层,沥青涂料应涂刷在洁净、干燥的底料上,常温下刷沥青涂料时,应在涂底料后12h之内实施;沥青涂料涂刷温度以200~230℃为宜。()
参考答案:错
____twice a year, whether it is a car or a bus or a truck, is the rule that every driver must obey in this city.
A.Examining
B.Examined
C.Being examined
D.Having been examined
凡士林为软膏剂基质,为改善其吸水性常加入的物质是()
A.石蜡
B.乙醇
C.羊毛脂
D.甘油
E.聚乙烯醇