为salerecord表GID字段添加外键，引用goods表中GID字段。

A、 ALTER TABLE salerecord ADD CONSTRAINT pk2 PRIMARY KEY(GID) REFERENCES goods(GID);
B、 ALTER TABLE salerecord ADD CONSTRAINT fk2 FOREIGN KEY(GID) REFERENCES goods(GID);
C、 ALTER TABLE salerecord ADD CONSTRAINT fk2 FOREIGN KEY(CID) REFERENCES goods(CID);
D、 ALTER TABLE salerecord ADD CONSTRAINT pk2 PRIMARY KEY(CID) REFERENCES goods(CID);