All staff members are reminded that you should not use the executive restroom （） you have written authorization to do so.

单项选择题Employees attending the writing seminar are expected to practice imaginative and （） writing as well as develop their technical writing skills.

A.detective
B.negative
C.descriptive
D.cooperative

单项选择题In order to be registered for our 5-year warranty, please send us the following postage-paid registration form （） 7 days of purchase.

A.by
B.until
C.within
D.before