Here's my solution. I only have 1 minute so please let me know if the logic is not correct.

We want to know if 1/(a-b)<b-a

In other words if (b-a)-1/(a-b)>0

or if (-(a-b)^2-1)/(a-b)>0

We can see that the numerator is definitely negative. So the only thing we need to know is if a-b>0

1) answers it. Therefore sufficient.

2) a-b could be negative or positive. Thus insufficent.

Therefore the answer is A.

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