若x-y=-1，xy=2，则xy-x+y=______．
xy-x+y=xy-（x-y），将x-y=-1，xy=2代入得：xy-x+y=xy-（x-y）=3．
As we all know, several primary schools and factories were named _____ the hero.
A．from
B．at
C．after
D．to
我国招标投标法规定，开标应由( )主持。
A．地方政府相关行政主管部门B．招标代理人C．招标人D．中介机构
