Answer:
The body of water remained part of the Byzantine Empire in 1360 CE is:
Step-by-step explanation:
The Propontide, as the Sea of Marmara, was known at the time, is an inland sea that unites two great seas: the Aegean Sea and the Black Sea, by means of the Bosphorus (which you can find in the right central area of the map ), since this sea is exactly in the division between Europe and Asia (place of the Byzantine Empire in AD 1360, its dominion continued being of said Empire during that period.