The correct answer is D) A small course change should work. The reason this is the correct answer is that shadowing effects on INMARSAT-B calls can often be overcome by simply adjusting the course of the vessel slightly to improve the line-of-sight to the satellite. Shadowing occurs when the vessel's position relative to the satellite is blocked by structures, landmasses, or other obstructions. By making a small change in course, the vessel can often maneuver out of the shadow and establish a clear signal path to the satellite, allowing the INMARSAT-B call to be placed successfully. The other answer choices are not as effective in dealing with shadowing. Turning on compensators (A) may help in some cases but is not a guaranteed solution. Selecting a different CES (B) does not address the underlying shadowing issue. Installing a shadow correction filter (C) can be helpful in fringe areas but is not always necessary for basic shadowing problems.