Quant flashcards 7-8 quiz, Q5

Can someone explain why the answer is D instead of A? Assuming that line L is y=x/2, we can assume that the point above it is of the form y=2x and the line below it is of the equation y=x/3.
Then, we see that the point above it, (a,b) will have b>an and the point below L, (c,d) will be of the form c>d. If we add the two inequalities, we’d see that b+c>a+d. There is also an ETS question of a similar format that I’m attaching below, please let me know why the correct answer to this question is D instead of A???


In the flashcards question, it says the slope is LESS THAN 1 which makes it different to the ETS example, where the slope is exactly 1, right?