有如下SQL语句 CREATE VIEW view stock AS SELECT 股票名称AS名称，单价FROM stock 执行该语句后产生的视图含有的字段名是_______。

A．SELECT 交易所,avg(单价)FROM stock GROUP BY 单价
B．SELECT 交易所,avg(单价)FROM stock ORDER BY 单价
C．SELECT 交易所,avg(单价)FROM stock ORDER BY 交易所
D．SELECT 交易所,avg(单价)FROM stock GROUP BY 交易所

A．ALTER TABLE stock股票名称WTIHC(10)
B．ALTER TABLE stock股票名称C(10)
C．ALTER TABLE stock ALTER股票名称C(10)
D．ALTER stock ALTER 股票名称C(10)