—Look! He’s running so fast!—Hard to______ his legs were once broken.
I ______ her not to walk on the thin ice but she wouldn’t listen to me.
Do you understand the theory ______?
If _____ for an explanation for an advanced camera, I would certainly find it difficult.
George would certainly have attended the meetings, _____.
He would have paid _____ for his fridge had the salesman insisted, because he really needed it.