According to the IBC, a soft story is a story in which the:
A- Lateral stiffness is less than 70% of that in the story above or less than 80% of the average stiffness of the stories above.
B- Lateral stiffness is less than 60% of that in the story above of less than 70% of the average stiffness of the stories above.
C- Lateral stiffness is less than 50% of that in the story above or less than 60% of the average stiffness of the stories above.
D- Story lateral strength is less than 80% of that of the story above.