Ammonia when used as a refrigerant is valuable because of its high efficiency, it is however ().
A. toxic
B. flammable
C. explosive
D. all of the above
前移式货架的货叉可以移动,而门架无法移动,所以作业受到一定限制。
A. 正确
B. 错误
依据《混凝土结构工程施工质量验收规范》GB50204-2015,7.2.3,按同一厂家、同一品种、同一技术指标,同一批号且连续进场的矿物掺和料,粉煤灰、石灰石粉、磷渣粉和钢铁渣粉不超过()为一批。
A. 100t
B. 200t
C. 500t
D. 1000t