In SC, "since" is not a sinonym of "because".
Only, in SC. Be careful!
Hmm..not sure if that is necessarily correct. Apart from the more commonly used meaning of 'since' that indicates 'starting from the time', the other meaning of 'since' is really very similar to 'because'.
It really is a moot point which one you would choose if we had two 'identical' options, with the only difference being 'because' and 'since'. GMAT cannot have two correct answer choices.
As has been mentioned, there are quite evident errors for which A should fall out of preference:
a. It appears that proper inflation of tires increases car-road friction
b. It appears appear as if 'owners' have 'tires'.
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