What immediate remedy can be used to correct shadowing of the satellite signal by a shipboard obstruction?

Correct Answer: Option A — Change the ship's course.

Inmarsat SES antennas require a clear line-of-sight to the satellite. If a shipboard obstruction, such as a mast or crane, shadows the antenna, the signal will be blocked. Changing the ship's course is the most immediate and effective way to restore the line-of-sight and re-establish the satellite link.