Final answer:
A 1-1/4 inch Bugle Head Type S screw is the correct choice for attaching single-layer gypsum panels to steel framing.
Step-by-step explanation:
The correct screw to use for attaching 1/2 inch or 5/8 inches of single-layer gypsum panel and base to steel framing is a 1-1/4 inch Bugle Head Type S screw. This screw is designed specifically for this purpose and is long enough to properly secure the gypsum panel to the steel framing without being too long that it might damage the integrity of the panels or not grab the steel adequately. The bugle head design helps the screw to sit flush with the surface of the drywall, providing a neat finish.