样板经淬火后的研磨量一般为（）。
A、0.2～0.4mm
B、0.3～0.5mm
C、0.03～0.08mm
D、0.7～0.8mm
参考答案：C
Before allowing goods to be exported, many countries in the world insist on（）which allows the goods to be exported and a compulsory legal document for export.
A．a shipper’s certificate
B．a mate’s receipt
C．a black list certificate
D．an export license
