I'm sitting at a keyboard/bar

I can't think unless I'm sitting at a __.

        (A) keyboard   (B) piano  (C) organ (D) bar


Hi,
The above is a multiple choice question for kids here. Which choice is the best to fit in the blank? Thanks.

I think (c) is clearly wrong, because it would  be "...I'm sitting at a organ."  Any of the others are possible grammatically, but I think "keyboard" is the most likely and "bar" is the least likely (especially if the question is in a test for children). 

Angliholic

Thanks, Huevos and Khoff.
Yes, I see eye to eye with you.
And the given answer is "keyboard." To make sure, does "sitting at a keyboard" imply "sitting before/at a computer?" Is it also right to say "sitting before a keyboard?"