The phrase 'offering a 'brief window of time' for humans to easily cross the sea'(5th paragraph) is closest in meaning to
A.
providing a panoramic view of the sea and an easier way to cross it.
B.
Only a small window zone of the sea as little as 2. 5 miles wide could be crossed.
C.
The descending supplied a temporary opportunity to cross the sea easily.
D.
The sea was as narrow as a window so that people could cross it without effort.