Engineers compare three methods to transmit a signal from one island to another 5 km away:
I. A submerged fiber-optic cable carrying infrared light.
II. A loudspeaker array broadcasting underwater sound.
III. A microwave antenna sending waves through air.
Suppose the ocean between the islands were completely removed, leaving a 5 km gap filled with vacuum while all equipment remains in place. Which of the methods, if any, can still deliver a signal across the gap?
a) Only III
b) Only I
c) Both I and III
d) I, II, and III