For every 100 automobile drivers who are involved in a

"evaluate the argument" : You need to find a seed, if known, could help in strengthening or weakening the argument
"resolve paradox" : You already have two opposite thoughts and you need to fill the gap that could help these opposite thoughts coincide together.

In this question, Complete argument is going in one direction, there is no opposite thought.

You have been given few probabilities (chances of happening A in the total number of chances), so that means you need to find if there could be anything (probability of occurrence of something else) which could strengthen or weaken the argument.
And because u need to find the probability, any choice that is mentioning only 'Number of one thing' can be ruled out. & here you are remained with 'A' and 'B'.

Now A can be chosen because it gives us an additional data about the probability of collision due to brake failure. If we know this probability, we would be able find out whether this probability is better than the probability(1/10,000) of malfunction of the new safety feature that is being claimed to reduce the probability of "brake - failure collision"