We may find that learning a foreign language does not have to be________learning our mother tongue,but can in fact be twice ________.
The book seems to have been _____ from various books and articles.
As more and more cars are produced and used, so the _____ from their exhaust-pipes contains an even larger volume of poisonous gas.
He left in such a hurry that I _____ had time to thank him.
There are usually at least two _____ of looking at every question.
It is not profitable to provide bus services in districts where the population is widely _____.