Can someone provide an explanation to the question?\

what is the OA?

OA is E.

http://www.manhattangmat.com/forums/each-of-the-25-balls-in-a-certain-box-is-either-red-blue-or-t308.html

DO NOT POST PROBLEMS AS IMAGE FILES UNLESS THE IMAGE FILES ARE NECESSARY. this means you should type out the words, unless the problem contains a diagram and/or contains awkward mathematical expressions that are difficult or impossible to type clearly (including roots and fractions). in those cases, it is ok to post an image file.

luckily, this is a problem that has been answered previously (see link above).
if you use an image file to post a problem consisting entirely of words, we will simply delete the thread.

thank you.