Final answer:
A starboard side daymark will show a fixed red light if lighted when entering from seaward.
Step-by-step explanation:
A starboard side daymark is a navigational aid used to indicate the starboard (right) side of a waterway when entering from seaward. When entering from seaward, a starboard side daymark will typically be square in shape and show a fixed red light if lighted.
Therefore, the correct answer in this case is A. show a fixed red light if lighted.