Jasper is a great painter. He is _____ Picasso.

A．as a great as

B．as great painter as

C．as great a painter as

D．so great a painter as

集中采购是指由政府设立的职能机构统一为其他政府机构提供采购服务的一种采购组织实施形式。实行集中采购的优点体现在( )

A．减低采购成本

B．便于实施统一管理和监督

C．采购周期长

D．取得规模效益