在紫外线照射下可转变为维生素D2的是() ["β-谷固醇","胆固醇","麦角固醇","脱氢胆固醇","胆酸"]
渐变流过流断面上各点的()近似等于常数。 ["['['p","

","

","

"]
孕期膳食中可能缺乏的矿物质主要是() ["钙、磷、铁","钙、铁、镁","锌、铁、钙","铁、铜、钙","硒、碘、钙"]
建筑基坑采用高压喷射注浆帷幕,对于黏性土基坑,当标准贯入锤击数N大于()时,最好采用复喷工艺。() ["10","12","20","24"]
建筑基坑采用高压喷射注浆帷幕,其注浆孔垂直度的允许偏差为()。 ["1%","2%","3%","5%"]
断路器切除故障时间包括断路器的()时间和()时间。