Question: What is the top selling brand of car?
Disambiguated questions and answers: question: What is the top selling make of car worldwide?
What is the top selling model of car worldwide?
What is the top selling make of car in the US?
What is the top selling model of car in the US?
answer: Toyota
Corolla
Ford
F-series
Natural Questions answer: Toyota (from the Wikipedia article "List of best-selling automobiles")