Now moving to choices,

(A) Refrigerators would not be made so that their
interior space is cylindrical.
YES. If interior space is cylindrical, then food cannot be pushed to corners, where it will remain out of sight.

(B) Refrigerators would not be made to have a
window in front for easy viewing of their
contents without opening the door.
Even if window is provided, food can be pushed to corners where it will remain out of sight.
(C) The problem of spoilage of refrigerated food is
not amenable to any solution based on design
changes.
Extreme assumption. A typical wrong choice. Anyways, the explanation is that possibility of design change to provide a solution is outside the scope of the argument. The argument discusses the effectiveness of only one solution.
(D) Refrigerators are so well designed that there are
bound to be drawbacks to any design change.
Similar to C
(E) Rotating shelves would be designed to rotate
only while the refrigerator door was open.
Similar to B. Food can still be pushed out of sight.