---How long do you think it will be _____China becomes a developed country?---At least 20 years, I guess.
When Peter speaks in public, he always has difficulty ______ the right things to say.
To avoid on how to use the word, you’d better refer to a dictionary.
According to a new survey carried out by an American university, learning______ second language can result in_______ increase in the power to learn your native tongue.
Mary, remember to bring the CD I want next time, _______?
Look! She is coming here and there _________.