So difficult______ it to acquire a large vocabulary without the help of a teacher that he was close to giving up .
It is clear that the whole world is passing through a social revolution in which a central _____ must be taken by scientists and technologists.
David paused to consult his notes, then_______ with his speech.
The policeman stopped him when he was driving home and _____ him of speeding.
_________ that he was in great danger,Eric walked deeper into the forest.
We finished the run in less than half the time _________.