Yanquan Is a Staunch Green Advocate

Yanquan is a staunch green advocate. He has been arguing with Marcela, who is a conspicuous consumer. In the course of their discussion, Yanquan is able to withstand the arguments Marcela offers for her position, and he does so in a strong and convincing fashion. He realizes afterward that his own counterarguments to Marcela's were pretty solid. Subsequent to this realization, Yanquan's attitude will

A) become less certain.
B) remain unchanged.
C) become more certain.
D) change to agree with Marcela.