一道英语题,为什么选C不选B

答案错了

decide on + n/动名词结构
eg： he has decided on （going there）/（that trip）.
decide to do 不定式结构 （非谓语）
eg：he has decided to go for a holiday.

另外 decide on 强调决定了什么事（可决定做可决定不做）
eg：he has decided on the complex decision which troubled him for a long time.
decide to do 强调决定了要做某事
eg：he decided to refuse her .

DECIDE ON 决定,选定 + 名词, 通常理解为“对什么作出决定” 而 on 是介词。
Examples:
1. Don't decide on important matters too quickly.
不要过于匆忙地对重要的事情作决定。
2. Decide on a career
选定一种职。
3. We'll decide on our team as and when we qualify for the competition.
我们来决定自己的队到什么时候才有资格参加比赛.
4. If you are not planning on breastfeed, you have to decide on a formula.
如果你不打算喂母奶，那麽你得决定选一种婴儿奶粉（水）。

decide to do sth 决定做某事
decide on sth 对。。。做出决定
所以选B

B
decide on是对...作出决定[决议]的意思
而decide to后面要接动词，也就是decide to do sth

decide to 只能加动词
decide on 接名词

固定搭配，decide to