( )是指购销商品、提供或者接受服务以及从事其他经营活动中，开具、收取的收付款书面证明。
A．支票
B．商业汇票
C．发票
D．收据
参考答案：C
牙纵折后最明显的症状是()
A．牙伸长感
B．咀嚼痛
C．牙叩痛
D．冷刺激痛
E．热刺激痛
Only then _________that he hurt her feeling.
A did he realize B had he realized C. he realized D. he had realized
D. he had realized