GMAT Verbal Section | Re: assumption question

What does the argument state -

Installing devices --> Most accidents would be prevented.

A - irrelevant to the argument above. Whether the device can be installed by trained or untrained people has no bearing on its effectiveness.
B - not relevant. the argument talks about the effectiveness of those devices. The amount of experience they have is irrelevant.
C - correct answer. Let us assume a value for seldom - say 1%.
Only about 1% of the time does a driver need to exceed the speed limit
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