In December, Tom-the-cat slept for exactly 3 weeks. Which calculations should we do in order to find how many minutes he stayed awake during this month? 
选项为:A:(31 - 7) x 3 x 24 x 60  B:(31 - 7) x 24 x 60  C:(31 -7 x 3) x 24 x 60  D:(31 -7 x 3) x 24 x 60 x 60  E:(30 -7 x 3) x 24 x 60  请回答其中一个选项.