preparing for=?

Mum is busy___dinner now.A.preparing B.preparing for为什么选A是否是因为B选项持续时间较长,还是?
感激不尽请晚上就回答,
1楼的朋友,我感觉你的回答不对,不好意思!准备某事和为某事做准备在中文还不是一样?准备做饭和为做饭作准备,在中文来说还不都是一样?希望有更好的解释!不管怎么样,谢谢1楼热心的朋友!

as follows,
接上面的
expenses, preparing for, made a study of, active, falls on, insurance, used to, keep in touch with, decorated, popular with, in order to, in fact, preparing for, is equipped with, are located in, attends, is covered with, take part in, attracted, join in, in addition, live with, in the center of, celebrate, make our rounds, take place
1. usually washers and dryers_____a common area in the building.
2. the singer is _____ the young.
3. he hopes that he can ______the international student games.
4. the christmas tree_____strings of coloured lights.
5. people wear glasses______see clearly.
6. today is tom's birthday, so we are going to ____it.
7. my parents and my grandfather all _____us.
8. the wedding party will _____next saturday.
9. the doctor_____the patient's case.
10. she received $100,000 _____ when her husband died.
11. i ____ go to the cinema a lot, but i never get the time now.
12. you can do the experiment_____
13. christmas day______december 25th.
14. while he was abroad on business, his company paid all his ______.

请教preparing for是现在分词做状语吗?做什么状语?
your friend is very busy preparing for her holiday.