IMO D

One thing is that rising here is incorrectly used, for this particular sentence, authorities will be worried about a rise in number of something, rising will be like its still rising
With this in mind, one can eliminate B and C

Now out of A D and E

A. being concerned about the rise in the number of car accidents and the average person’s attention span being shrunk gradually
They are not in a process of(being, generally means this) getting concerned, this not even parallel.

D. concerned about the rise in the number of car accidents and the gradual shrinkage of the average person’s attention span
They are concerned about two things
1) rise in the number of car accidents
2) the gradual shrinkage of the average person’s attention span

E. given that they had been concerned about the rise in the number of car accidents and the gradual shrinkage of the average person’s attention span as well
as well in the end breaks the parallelism.
_________________

If you notice any discrepancy in my reasoning, please let me know. Lets improve together.

Quote which i can relate to.
Many of life's failures happen with people who do not realize how close they were to success when they gave up.

concerned is that only past participle in option D that can work as a modifier to noun activist

So Ans is Option D