When you submit a question like this, it's best to include the structure. Not including the structure is like asking the question, "What flavor is it?" when there is nothing in perspective.
So, let's focus on glucose. What can you do to it to decrease the maximum number of stereocenters? What chemistry do you know that can do this?
P.S. I'd be very likely to put a problem like this on an exam because it requires thought, not memorization.