用字母表示乘法的交换律为______．
乘法交换律：ab=ba；
故答案为：ab=ba．
B2B支付业务工具方式仅为（）
A、电子支付卡
B、证书支付
C、国际卡
D、贷记卡
Supporters of underground development say that building down ____ building up is a good way to use
the earth's space. [ ]
A. other than
B. besides
C. rather than
D. except for
