Answer: Demasiados
so you want to know what means what.
Your stuck between Demasiados y Bastantes
These two are very go chooses but they have slightly different meanings
Demasiados means too many
bastantes means enough
looking at the sentence
it says "If you ONLY(key word) need one pencil and someone gives you 20, you have...enough or too many pencils?
If you only needed one Think about it you ONLY NEED ONE but now you have 20 You dont need the other 19 pencils so ANSWER WILL BE
TOO MANY
you have too many pencils becuase u only need one
