______ without friends ______ the most difficult challenge for Chuck while living on the island.

I hope you have a great trip to Hong Kong. —________.

Do you mind opening the windowthe air inside is not so fresh.— __________, Mr. Smith is taking a nap (小睡)，don’t make him catch a cold.

I could not start my car this morning due to the cold weather. –No wonder you were late. You ___ have used mine. I was not using all the morning.

These are the words ____ you must attach greatimportance when you write the essay.