The correct answer is A) tapering the upper guides and building up the teeth. During a long ocean tow of a jack-up, the clearance in the upper guide should be reduced to zero to restrain the leg and eliminate the impact loads from dynamic responses. This is best achieved by tapering the upper guides and building up the teeth, as this allows the leg to be securely held in place and prevents excessive movement that could lead to impact loads. The other options are incorrect because: B) removing certain lengths of the leg would not adequately restrain the movement, C) raising the spud cans into hull recesses would not address the clearance in the upper guides, and D) lowering the spud cans below the hull would not restrain the leg's movement during the tow.