Weaken
Henry says that electric engines (cars) pollute less than combustion engines. Therefore, switching from regular cars to electric cars would reduce urban pollution.
This isn't a terrible argument. Car engines are a major contribution to pollution. But, Henry hasn't given an exhaustive (hehe) account of the situation. What if the production of electric engines is way more polluting than the production combustion engines? Sure using electric engines is less pollution but you gotta make them in the first place and that could tip the scales.
Umit doesn't go there, though he could have. He brings up another consideration that Henry overlooked. He reminds us that electric engines run on batteries that need charging. Charging all those batteries places greater demand on power plants which then will generate more pollution as a result.
Okay, yeah, that's a good point Umit! You did a good weakening on Henry's argument by pointing out something Henry overlooked (i.e. assumed wasn't an issue). Henry, batteries don't power themselves okay? You gotta charge them you dodo!
Alright, so now we have to do another 180 and weaken Umit's argument. We have to see that Umit assumed that the extra pollution generated by the power plants is relevant. (A) gives us a reason to think that it's not relevant. If it's true that power plants are not near major cities, then does their pollution even matter? Henry was only concerned about urban pollution after all, not pollution in the entire country or on the whole planet. (A) may as well have told us that these power plants are on Mars.
(B) is an attractive trap. It says that the additional units of pollution from the power plants would be "offset" by the decreased units of pollution from the electric engine cars. Okay, "offset" by how much? Entirely offset? Or just somewhat offset? We're not sure. So it could be on a range anywhere from entirely offset to just somewhat offset. But anywhere on that range is bad for Henry. Even if it's entirely offset, then that just means switching to electric cars is no better than not switching in the first place. Henry actually needs switching to electric cars to be better for urban pollution. Not just neutral.
What (B) needed to say is that the additional additional units of pollution from the power plants is only a tiny fraction of the total decreased units of pollution from the electric engine cars. In other words, power plants are generating +1 unit of pollution but electric cars are saving -10 units of pollution. That would help Henry and hurt Umit.
Olson: Given that the oldest primate fossils discovered so far date back only 55 million years, your estimate of how long primate species’ development has gone on is sheer speculation.