题目内容：

[单选题]Once a man and his wife worked for a businessman． There was a big box in the business-man-s living room． The businessman pointed at the box and said，"There's only one thing you(11) do．Don't open the box． After saying this，he(12)the living room．

The woman said to her husband，"There (13) be something expensive in the box． Let's (14) it，shall we? Her husband said no to her．

The woman didn't give up her (15) = One day，she decided to find out what was (16) it． Her husband didn't stop her． She opened the box and looked (17) ．She found nothing in the box and tried hard to close it，(18) she failed．

That evening the businessman came home and found the box was (19) ．' He was Very an gry and asked the woman and her husband to leave his home．

"But there was nothing in the box， the woman said． "We haven-t taken anythiny (20)．"The businessman shouted at them，"The box is not important． I cannot believe you．That’s important!" '( )11．

A． needn’t

B． wouldn’t

C． mustn’t

D． shouldn't