耦合用于衡量一个模块内部的各个元素彼此结合的紧密程度。
参考答案：错
Red is usually_______danger so traffic lights include red ones. [ ]
A. marked with
B. lined with
C. related with
D. associated with
用无水Na2CO3来标定0.1mol/L HCl溶液，宜称取Na2CO3为( )。(M=105.99g/mol)
A．0.5～1g
B．0.05～0.1g
C．1～2g
D．0.15～0.2g
