The sentence that best fits is "Things aren't always what they seem" (option d).
The phrase means that we should not be guided by how things look because they can look like one thing and be something else entirely. According to the above, we can see a person who appears to be very nice and is actually very mean.
These two sentences are related because an old person is supposed to be a kind and friendly person, generally old people are vulnerable because of their age. However, some old people can be terrible for their negative actions.
According to the above, we can infer that both refer to the fact that something can be pretended but that the attitude is not in accordance with the appearance of the individual.
Learn more about appearance in: https://brainly.com/question/17723129
#SPJ1