单项选择题
No credit will be offered（）you place an order for more than 40.000 units.
A. after B. when C. if D. unless
单项选择题 A:Good weekend? B:（）
单项选择题 Mr. McNeil asked Mr. Don Bradley to ship the goods（）air.
单项选择题 （）the Manager’s not available at the moment. But the Assistant Manager is here.How Can I help you, madam?
