---You may find the key to the maths problem on page 107. ---Ah, it’s so simple. I wonder why I ________ of that.
He is a man of few words, and seldom speaks until _______ to.
Having a trip abroad is certainly good for the old couple, but it remains ______whether they will enjoy it.
The more you practise _____ English, the better your _____ English will be.
The flowers ________ sweet in the garden look ________ and attract the visitors to the beauty of nature.
The possibility of a murder _____, the police have set about looking for the clues to her suicide.