Is it E?

yes it's correct...

nor are they making

confused me...

can you explain how did you land to answer E

'That' is required after indicates. C, D and E remain.
C - 'nor' requires neither. The correct idiom is 'neither X... nor Y'. 'there are few people who have' is wordy and awkward
D - 'have reduced' is not parallel to 'making'.
E - 'have reduced' is parallel to 'made'

Option A. 'nor are they making' this statement is not correct because 'nor' must appear with 'Neither'
Option B 'having significantly' this is an inappropriate word combination ,it does not follow.

Option C. This is similar to the error in option A 'nor' cannot appear in a sentence without Neither preceding it .

Option D. This is the not correct answer 'that few people have significantly reduced the amount of driving they do and are not making' this option is the most suitable to the question.Since the prices of energies have been tripled,few people reduced the amount of driving they do AND ARE NOT MAKING(this contradicts the fact that energy prices are high).

Option E. Here,'that few people have significantly reduced the amount of driving they do OR MADE.
in layman explanation,since energies price have been tripled they Either reduced the amount of driving OR made fuel efficiency a priority when shopping.