The heat was already overwhelming and lasted a week, which duration made it seem sheer torture.
a. overwhelming and lasted a week, which duration made it seem
b. overwhelming, and because of lasting a week, it made it seem
c. overwhelming and lasted the duration of a week to make it seem
d. overwhelming, and its lasting a week made it seem
e. overwhelming and, by lasting a week, making it seem
I thought the answer is either b or d, and the answer is d. Why is b wrong and how I can make b right?