Answer:
The correct answer would be - by the suffocation
Step-by-step explanation:
As it is mentioned that the mansion has 7 feet window but it was open so there are no chances of the broken glass and it was the thunderstorm which means there was wind, not rain so where did the water come from?
To understand it assume Bill and Susie were not human but a pet, so having no clothes can be justified now water and glass so what pet have a connection with water so it is fish that leads to other clues broken glass that could be the fishbowl.
So, The storm winds blew open the window, which knocked their fish bowl off the table, and it crashed onto the floor and died with suffocation.