The headmaster thought _______ necessary to invite Professor Brown to give us a lecture.
—Ann is in hospital. — Oh, really? I __ __ know. I __ __ go and visit her.
When he the door, he found his keys were nowhere.
Every evening after dinner, if not from work, I will spend some time walking my dog.
The loss has not yet been ______ accurately, but it is believed to be well beyond a hundred million dollars.
—Why does the lake smell terrible? —Because large quantities of water in the lake .