John waited at the bus-stop for nearly half an hour _____ the bus finally arrived .
He could see the tall chimneys of the factory________.
________matters most in learning English is enough practice.
It is the Chinese custom to ________ for family unions on Mid Autumn Day.
You ________ touch the chemical, or you ________ get burnt.
I ________ work out the problem at first, but after my teacher showed me an example, I ________ get the answer easily.