GMAT Critical Reasoning (CR) | Some private taxi drivers in Crimea equipped their cars with air condi

Narrowed the answer choices down to A and D, and went with D. Here'swhy:

Taxi Drivers
Some installed A/C units -> led to happy customers -> resulted in more tips >>>> Conclusion: ALL cabs get A/C = bigger tips for ALL cabs

Right off the bat a red flag goes off- just because some cabbies got received higher tips does not mean a mass installation of A/C units will result in more tips for everyone. Remember, correlation does not imply causation. As this is an assumption question,
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