IMO C
Conclusion talks about opposing recent guidelines that would require us to produce cars with higher fuel efficiency. The reasoning is flawed because author considers previous attempt the only way to accomplish fuel efficiency vehicles.

(A) Even after 1977, large automobiles were frequently involved in accidents that caused death or serious injury. (This does not discuss about recent guidelines and thus , does not weaken opposition to recent guidelines )
(B) Although fatalities in accidents involving small cars have increased since 1977, the number of accidents has decreased. (irrelevant)
(C) New computerized fuel systems can enable large cars to meet fuel efficiency standards established by the recent guidelines. (There is an alternative way to accomplish higher fuel efficiency standards established by the recent guidelines.)
(D) Modern technology can make small cars more fuel-efficient today than at any other time in their production history.(does not weaken opposition to recent guidelines )
(E) Fuel efficiency in models of large cars rose immediately after 1977 but has been declining ever since. (supports the argument)

ranjithreddy.k9 wrote:Auto industry executive: Statistics show that cars that were built smaller after 1977 to make them more fuel-efficient had a higher incidence of accident-related fatalities than did their earlier larger counterparts. For this reason we oppose recent guidelines that would require us to produce cars with higher fuel efficiency.
Which of the following, if true, would constitute the strongest objection to the executive's argument?
(A) Even after 1977, large automobiles were frequently involved in accidents that caused death or serious injury.
(B) Although fatalities in accidents involving small cars have increased since 1977, the number of accidents has decreased.
(C) New computerized fuel systems can enable large cars to meet fuel efficiency standards established by the recent guidelines.
(D) Modern technology can make small cars more fuel-efficient today than at any other time in their production history.
(E) Fuel efficiency in models of large cars rose immediately after 1977 but has been declining ever since

B looks a bit tempting, but I think it partially weakens
the latter part of option B "...the number of accidents has decreased"
I think that part doesn't clearly say the number of small car accidents has decreased.
If total car accidents = 100 ; large cars = 40 , small cars = 60
Now, total accidents = 90 ; large cars = 30 , small cars = 60
C is only choice that can be considered better because
Conclusion : oppose recent guideline because it leads to increase in fatalities
Weakening statement : New computerized fuel systems can enable large cars to meet fuel efficiency standards established by the recent guidelines.

the point of focus here is the fuel efficient cars.

B and C are close calls.

B misses because it takes into consideration the accidents. POE.

C gives reason that fuel efficient cars can be made.More so the cars can be bigger too.

Here is an example of a shift in language.

It starts by saying that "smaller cars" have a higher incidence of fatalities. Then it says "higher fuel efficiency" as if "smaller" and "higher fuel efficiency" are exactly the same.

Answer choice C points out that these two terms are not necessarily the same.

Going with C here!!...Let me put my point to show why B is wrong. It is explicitly mentioned that the executive is indifferent to small cars because of a higher incidence of accident-related fatalities(not accidents )...So I would say that he is bothered not about the accidents but about the accident-related fatalities.

I hope that gives a good enough reason to reject B.