The boy was sitting _____ his mother, _____ his back _____ the door.
The scientist’s many years’ careful observation ____ a surprising discovery.
Don’t come and see me today – I’d rather you ____ tomorrow.
It is clear that your ____ English will greatly improve if you can practice ____ wherever you can.
This means going back to the place where we left the family ____ in a tree the night before.
Most birds find it ____ to sleep in the trees.