Demario's wife, marta, asks him if he wants some cutting the grass and weeding the garden. he declines the offer and feels "blue" for the rest of the day because he keeps thinking, "marta thinks i am getting older and losing my physical abilities." what type of cognitive distortion is involved here?

I believe the answer is: arbitrary inference
arbitrary inference refers to the process of creating a conclusion without sufficient evidences to back it up.
We can see this arbitary interference by observing marta's thought that believe Demerio is older and losing my physical abilities without even seeing him doing the task.