We do not allow ______ in the lecture hall, so you are not allowed ______ here.
It is generally believed that teaching is ______ it is a science.
He raised his voice to make himself _______ clearly by the audience.
There were too many people in the room and he could hardly find a chair ______.
Rather than ______ on a crowded bus, he always prefers ______ a bicycle.
They hurried to the station only _______ that the train had left.