Twenty-five percent of the water in this river _____ dirty in the past.A. is B are C. was D. were
I have no brothers ___________sisters.
How many ____ are there in the picture?
Tom is in Class 1 and I am in Class 2. ______ are not in the same class.
—Are there _______ halls in the building? —Yes, there are _______.
----________ is your friend ? ----He is a worker .