—Always look around________you cross the street,David.—OK,I know,Mom.A.untilB.beforeC.unless
A: Are there ____new pens in your pencil--box? B: Yes, there are ____.
A: When do you usually have dinner? B: ____6:30____the evening.
I like English, ____ I am not good at it.
There is ____ office on _____first floor.
A: Is the pen on the desk? B: ____.