following a 'don't solve' approach, we can see that the question is focused on ratios (i.e proportions of a mixture) and needs the relationship between flour and sugar to be expressed in terms of a multiplier, fraction, percentage or two fixed values for the quantities involved.
1) sets out a relationship between the only two ingredients of the mixture, based on percentages *sufficient*.
2) sets out a relationship on a numerical value. For a proportion this won't work, as 1.5 cups to 3 cups is a very different proportion to a possible 100 cups to 101.5
A is your answer and hopefully without pausing to work out all the numbers you have banked yourself a minute or so extra for later in the quant section
(though with your having a Q50, I'll be the one asking your
Blogging my way through the applications/study process!!