______ do you visit your grandparents— Every two weeks.

Facebook is one of the most popular websites in Britain ___ over twenty-five million users.

Your trousers____ dirty.You must have____washed.

Nobody could understand her though she tried to her idea by using the simplest English, because they are foreigners.

（题文）(2015·北京)___________the early flight, we ordered a taxi in advance and got up very early.