Question

insert one comma to separate the coordinate adjectives.
for their vacation, vijay and tessa rented a small beach bungalow, but the unanticipated fast - approaching hurricane forced them to evacuate and end their vacation early.

Explanation:

Coordinate adjectives modify a noun independently and can be separated by a comma. "Unanticipated" and "fast - approaching" both modify "hurricane" and are coordinate adjectives.

Answer:

For their vacation, Vijay and Tessa rented a small beach bungalow, but the unanticipated, fast - approaching hurricane forced them to evacuate and end their vacation early.