The goal here is to first look at the question stem - "Which of the following is an assumption on which the stickler’s argument depends?"
The argument that Stickler makes is that red velvet cake contains cream cheese by definition and since vegan cakes would not contain any it should not be referred to as red velvet cake.
So, lets apply process of elimination (PoE) here:
a. Cream cheese is defined not by its taste, but by its composition. - this assumption would help Stickler's argument.
b. Red velvet cake must contain milk. - this assumption is irrelevant as it is not associated with cream cheese. This choice can eliminated
c. Any vegan cake ought not to take the name of its non-vegan counterpart. - Stickler makes no argument about any other cake other than red velvet which makes this statement too broad. This choice can be eliminated.
d. A proper red velvet cake has a white, creamy appearance. - this assumption is irrelevant as it is not associated with cream cheese. This choice can eliminated.
e. The amount of cream cheese in a red velvet cake is not variable - even though this is related to cream cheese it does not help the argument. This choice can be eliminated.
The answer is A.
Hope this helps!
Lighthouse Prep