In the retail clothing industry, the spring months are traditionally weak, because revenues are low and advertising expenses are high as retailers prepare for the heavier back-to-school and holiday shopping seasons.
(A) low and advertising expenses are high as retailers prepare
-------- "ARE LOW" and "ARE HIGH" are parallel -> Looks okay, let's keep it.
(B) low and their advertising expenses are high as they prepare
-------- Use of "THEIR" makes the parallelism flawed
(C) low with higher advertising expenses in preparation
-------- "LOW WITH HIGHER ADVERTISING" -> What does this even mean? Non-sensical -> Reject
(D) low, while advertising expenses are higher to prepare
-------- Usage of "WHILE" is usually done to showcase contrast/change in flow. Moreover, "HIGHER TO PREPARE" is not making any sense
(E) low, while their advertising expenses are higher in preparation
------- "THEIR ADVERSITING EXPENSES ARE HIGHER" -> This is an Independent clause and cannot be connected by using "WHILE" -> Drop E
A must be the right answer
I hope this explanation helped you.