They dug into the hill.
They did not/didn't dig into the hill.
Mary bought a dress from the store.
Mary did not/didn't buy a dress from the store.
The students (be) hungry.
The students were not/weren't hungry.
I lay down for a nap.
I did not/didn't lie down for a nap.
The boy (be) short last year.
The boy was not/wasn't short last year.
Yesterday, I fed my dog outside the house.
Yesterday, I did not/didn't feed my dog outside the house.