分类：教育/科学-外语学习
问题：请帮我看一下这道六级听力题iftomandMarrydon'tc 
if tom and Marry don'tcome to the party, I'll have 13.M: Let's inve two more just in case.Q: If everyone comes, how many will be at the party?(A) 13  (B) 17  (C) 30  (D) 15 
回答：17,不要想得太复杂