It's impossible that he knew the problem ---- HE ............. THE PROBLEM
HE CAN'T HAVE KNOWN THE PROBLEM
It was careless of him to go without checking the time. --- HE ____________ THE TIME BEFORE GOING
He SHOULD HAVE CHECKED the time before going.
We have bought more food than was necessary for the party ---- WE _______ FOR THE PARTY.
WE NEEDN'T HAVE BOUGHT MORE FOOD FOR THE PARTY.
Perhaps they came up with a better solution last night. (MAY) --- THEY _________ UP WITH A BETTER SOLUTION LAST NIGHT.
They MAY HAVE COME up with a better solution last night.
When she was ten years old, she had the ability to read people's minds. ----- SHE__________________ PEOPLE'S MINDS WHEN SHE WAS TEN YEARS OLD.
She COULD READ people's minds when she was ten years old.
I'm sure they didn't phone you --- THEY __________ YOU.
THEY CAN'T HAVE PHONED YOU.
It's just possible that he went to bed early. ---- HE ________EARLY.
HE MIGHT HAVE GONE TO BED EARLY