I ran into the same problem three years ago with a student whose vision problems were so bad he had to get within six inches of the monitor to see anything at all. I never figured out a way to dow what you're asking, but did come up with an alternative work around.
I wound up having to make sure he was always seated at one of the few 24 inch monitors in my lab, which by itself was not enough. I had to also teach him how to use the Ctrl+ (control key and plus sign) key combination to zoom in so that he could read onscreen content.
Using the control and plus key zooms in making everything larger, including the drop-downs you mention, so you don't have do anything special to your questions and answers. Ctrl- zooms out.