A ______ is something we buy to help remind ourselves of a place we have visited.
Paper produced every year is ______the world’s production of vehicles.
We had a long way to go, and the snowstorm ________ our difficulties.
--May I open the window? It’s too hot. --_____________.
John began to study French last Sunday. ____________
Some plants are so difficult to grow that they can only ______ in a perfectly clean environment.