He was so deep in thought,thinking of the problem ________ he knocked into the tree without noticing it.
--- Can I help you? --- Yes. I bought an iPhone 6 here last week, but there _______ something wrong with it.
He promised that he ______ us in the party, but he hasn’t turned up until now.
There are about one million words in English. ________, most people use only about ten thousand of them.
---Mr. Jones isn’t at his desk. Where is he? ---_______. I have no idea.
A smile ______ the mother’s face when the son walked onto the platform to receive the prize.