多项选择题以下属于供应商单证的是（） A、送货单 B、运单 C、原产地证明 D、入库通知单
单项选择题Internal economies of scale arise when the cost per unit （ ） A、rises as the industry grows larger B、falls as the industry grows larger. C、rises as the average firm grows larger. D、falls as the average firm grows larger.
