易切削结构钢的牌号如何表示?
参考答案:
如Y12表示平均含碳量为0.12%的易切削钢;Y40Mn表示平均含碳量为0.40%,含锰量较高的易切削钢。
下列离子方程式书写正确的是( )
A.铜屑中加入足量氯化铁溶液:Fe3++Cu=Fe2++Cu2+
B.大理石中加入足量浓盐酸:CaCO3+2H+=Ca2++CO2↑+2H2O
C.硫酸溶液中加入足量氢氧化钡溶液:Ba2++OH-+H++SO 2-4=BaSO4↓+H2O
D.碳酸氢铵溶液中加入足量氢氧化钠溶液:HCO -3+OH-=CO 2-3+H2O
During the festival the town holds________traditional activities including temple fairs(庙会)to bring
tourists back to scenes of ancient times.[ ]
A. a collection of
B. a range of
C. a kind of
D. a bunch of