I chose C, but not for the reason Kevin described. Would it have been reasonable to have picked C because if the cratering from the LHB would kill any existing life on earth, and we are currently alive on earth, the LHB must have decreased in intensity? @Kevin_Lin

I cannot understand how he is right when he says "Each time there was a doubling in cost, oh, look, there was a doubling in the number of transistors in those chips. ya that must be true." when explaining D.

This feels like he's committed the "most classic trap". The only information he has is that a doubling of transistors means a doubling of cost, not the doubling of cost means the doubling of transistors. He gets the problem right but seems to explain it wrong.