Although energy prices have tripled in the United States over the last two years, research indicates
few people to have significantly reduced the amount of driving they do, nor are they making fuel efficiency a priority when shopping for cars.
A. few people to have significantly reduced the amount of driving they do, nor are they making - indicates should be followed by that
B. few people having significantly reduced the amount of driving they do or made - indicates should be followed by that
C. that there are few people who have significantly reduced the amount of driving they do, nor having made - Parallelism issue
D. that few people have significantly reduced the amount of driving they do and are not making - "Few people ... are not making fuel efficiency a priority".
Which means that most people are making fuel efficiency a priority. That's precisely the opposite of the desired meaning. the two things being studied are presumably simultaneous -- they're in the same study, regarding the same consumers -- so the sentence is most sensible if the tenses are the same.
E. that few people have significantly reduced the amount of driving they do or made - Correct
Answer E