Can you please tell me what's wrong with this sentence? ?

the sentence is :
I'd choose playing the guitar,bicycling and cooking as best

my teacher told me something is wrong with the part " as best "
what should it be ?
thanks

yeah...
I was wondering if I should say:
the best or the bests or bests ????

the sentence is meant to be "i think playing the guitar, bike riding and cooking as the best hobbies"

When you just say "as best," the sentence is ambiguous. It's ambiguous because you aren't mentioning the subject. As best of what? You can possibly say that those three activities are the best of your hobbies. You could write it like this:

"I'd choose playing guitar, bicycling, and cooking as best of my hobbies."

Including "the" in between "as" and "best" makes the sentence sound a lot better. However, either way, including "the" doesn't necessarily seem like a major concern in your sentence.

It's a brief and short answer, but I hoped this helped you.

I think your teacher wants a determiner in front of "best". Like this:
"I'd choose playing the guitar, bicycling and cooking as the best".
However, it isn't really needed, but it adding "the" makes the sentence sound better; the original sentence is not wrong though.

I agree. If you have already established, in a prior sentence, that you'd rather be doing those activities then you should be able to put a period after "cooking".

I'd choose playing the guitar, bicycling & cooking as my favorite things to do

or

You need something after the best

as the best thing to do while I'm bored
or as the best hobby
or as the best past time

What are you trying to say or mean? Add THE after cooking:

I'd choose playing the guitar,bicycling and cooking as THE best