Hurry up! Mark and Carl us.
We arranged to meet at the cinema at 7:30, but he failed to ______.
Miss Green contributed fifty dollars, but she wished she could contribute _____.
When _____ different cultures, we often pay attention only to the differences without noticing the similarities.
Hundreds of species are declared to _____ in the coming century.
It was playing computer games ____ cost the boy plenty of time ____ he ought to have spent doing his lessons.