Read the following two arguments about school uniforms then answer the question below.

Carl: "Imagine a world without color and free choice. That will be the world we live in if we are forced to wear uniforms. The uniforms will be ugly. They will make you look like a nerd, because uniforms are what all nerds wear. Don't be one of the fools that thinks this is a good idea, because everyone knows we do not need uniforms.

Beth: "Uniforms are a great idea for our school. Studies have shown that schools that adopted a uniform saw a 10% increase in grades. I know Carl says that the uniforms are ugly, however as a guy, what does he know about fashion? The uniforms will not be ugly, because uniforms are not ugly."

Who uses assertion in their argument?