Critical Reasoning

Automobile Dealer's Advertisement:
The Highway Traffic Safety Institute reports that the PZ 1000 has the fewest injuries per accident of any car in its class. This shows that the PZ 1000 is one of the safest cars available today.
Which of the following, if true, most seriously weakens the argument in the advertisement?
(A) The Highway Traffic Safety Institute report listed many cars in other classes that had more injuries per accident than did the PZ 1000.
(B) In recently years many more PZ 1000's have been sold than have any other kind of car in its class.
(C) Cars in the class to which the PZ 1000 belongs are more likely to be involved in accidents than are other types of cars.
(D) The difference between the number of injuries per accident for the PZ 1000 and that for other cars in its class is quite pronounced.
(E) The Highway Traffic Safety Institute issues reports only once a year

OA C, Explanation says that class of PZ1000 is more likely to have accidents and hence no of accidents of PZ1000 can be more than accidents in other cars. Here explanation says that cars other than PZ1000 may have less accidents bUT we are talking about injuries/accidents and NOT no of accidents.
It can also be understood like this:
Since class of PZ1000 is more prone of accidents and PZ1000 still has least no. of injuries/accident in its (i.e most dangerous) class then it is safest of all cars. Hence C is slightly strengthening the arg.

ACTUALLY, i think the option C only allows to infer that given conclusion CANNOT be concluded BUT option C DOES NOT weaken and therefore following option would be equally likely to be correct answer because we want some option to highlight that we cannot infer safest car among cars of ALL classes by basing our point on one class
OPTION: Cars in the class to which the PZ 1000 belongs are LEAST likely to be involved in accidents than are other types of cars