A.(X>Y)AND"BEIJING"$"BEI" B.(X<Y)AND"BEI"$"BEIJING" C.(X>Y)OR"BEI"$"BEIJING" D.(X<Y)OR"BEIJING"$"BEI"
A."變量" B.常量 C.{無效} D.(參量)
A.1 B.-1 C.F D.T