－How many _____ are there in the box？－Oh, there’re four.

______ is very difficult.

 Professor Li gave us a very useful ________ on how to prepare for the exam.  

----I hear you have to get up early every morning . ----Right . It is one of the _______ in my family .

— You look so healthy!— Yeah, I like eating apples. An apple a day keeps the _________ away.