当你早上遇见老师的时候,你应该说________。
There are some _______in Dayton Art Museum ,For example, no food or drinks is allowed inside.
Cathy was very happy to meet _____old friend on the plane to Paris.
--What about having a drink? --_______.
They usually go shopping____ their lunch break.
After Steven sent some e-mails ,he______ surfing the Internet.