They were surprised that a four-year-old boy should work out such a difficult problem ____ they themselves couldn’t.
It is the teacher ____ taught me when I was a child ____ I am going to visit.
She won’t leave the TV set, ____ her husband is waiting for his supper.
— ____ makes her different from the other students? — Honesty, I think.
He went home for lunch ____ the clock struck twelve.
19. Is this the very factory ____ he visited last month?