to be and being are always discouraged at GMAT...I narrowed down to d and e and picked up e.

E sounds passive but still fit the bill.

in D, shoppers has been changed to A shopper....would appreciate if someone can explain it.

the question would simplify if u know this idiom: to think of X as Y.

a. Shoppers may not think of autumn to be [ does not follow the correct idiom]
b. Shoppers may not think of autumn being [ idiom not maintained]
c. A shopper may not think of autumn being [idiom not maintained]
d. A shopper may not think of autumn as [correct!]
e. Autumn may not be thought of, by shoppers, as[ idiom not mintained]

Thanks for the clarification. Really appreciate that.

the logic is to understand the case of subject and object
shopers(plural) can't buy a swimsuit(singular)
but a shopper can buy a swimsuit
hence A and B is out ; E is way out
B/n C and D being is passive in C

hence D