Li Lei can’t go hiking with us today,because he take care of his sick mother.

I want to know more __________about how to use this word.—You can look it up in the dictionary.

What______useful dictionary for beginners of English! Where did you get it?— I bought it in the bookshop.

Premier Wen Jiabao started his three-day official visit to South Korea, ______ was aimed at increasing cooperation and good neighborliness.

We find impossible to finish the work in a week.