total sales =100 (previous year)
as per option A, LY total sales =109 (assume it is 9%)

PY French fry sale = 50
LY French fry sale = 55(50*10%)

so other items sale
PY =50
Last year = 54 (other sale item 8%)

Compare to 8% sale of other item, 10% sounds good to me. so it is wakening the claim that the change has hurt sales of Fast Fries. Actually it didn't.


So option A

The argument is that using the more healthy oil did not impact sales negatively.
This is supported by the fact sales increase by 10% over the previous year since the oil change

We are then asked to support this.
A is correct because comparatively we can eliminate any other factor that may have increased sales of fries e.g. sales of burger +Fries combos. Since other foods did not increase more than 10%, but fries did, we could reliably conclude that the sales weren't impact negatively.
B comparison between Soft drink + fries is irrelevant to fries oil changes.
C this directly weakens the argument as it states that customers prefer the old oil.
D is incorrect. If the number of customers increased by 20% from the year before the oil change was made, but the sales only increased by just over 10% then this would weaken the argument as we would potentially expect a commensurate 20% increase in fries sales. Since this didn't happen we can eliminate this answer. D is also a typical 'confuse you with numbers instead of percents used in the stem' type question
E is incorrect as it weakens the argument for similar reasons to D