. ________ when the boulders suddenly disappeared.
You’d better not call the manager between 7 and 8 this evening, for he ________ an important meeting then.
— Have you read the novel? — Yes. I ________ it three times while I was in university.
Every means _________, but none proved __________.
The time and effort he has devoted during the past few years________ trees in that remote area is now considered to be of great value.
Sometimes smiles around the world _________ be false, hiding other feelings like anger, fear or worry.