采用凭样品交货时，为了争取国外客户的订单，应选择质量最好的样品给对方，以达成交易()。
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在实际业务中，如买方未按合同规定时间开立信用证，卖方必须进行催证工作()。
牙釉质粘接剂可分为两类，即_______和_______。
Weaker bonds to dentin are caused by one of the reasons that()
A. dentin contains more mineralized tooth structure than enamel
B. dentin contains more water than enamel
C. the smear layer makes wetting by adhesive more effective
D. fluid m the dentin tubulesreduces the stability of the composite resin to dentin bond
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