c)
He had been knocking for some time before a servant opened and asked what he wanted.
1)are not sitting
2)am having
3)is the dog swimming
4)are enjoying
5) isn't writing
I can eat potatoes.
You can swim in the pool (swimmingpool).
I like to walk with my dog.
Look! It's a little mouse. (there)
Look! Big frog. (right there)
Frogs can jump. (High)
Don't worry! You're a big boy.
She hasn't made this mistake before
Peter and Jane haven't had a long walk today