Which sentence provides the BEST evidence to support a reader's inference that Robert is stubborn?

A
"According to this cartoon in the newspaper, astronauts can see the Great Wall from the moon."

B
"But my teachers at school showed us this cartoon and discussed all the important things that you can learn in a newspaper."

C
"But I still want to believe the cartoon," began Robert.

D
"I still believe the newspaper," Robert insisted.