Which of the following is a respectful way to express your opinion?

“you obviously didn’t listen.”

“you don’t know what you are talking about.”

“i disagree. in my opinion, the first example is better than the second.”

The last one. "I disagree. In my opinion, the first example is better than the second.

“I disagree. In my opinion, the first example is better than the second.”
Telling someone they "obviously" didn't listen is not respectful, nor is it helpful, as well as telling someone they don't know what they are talking about.
However, telling someone you disagree with their opinion and telling them what you think is not disrespectful in any way.
Hope this helps!

99, multiply all the sides

The setting is new mexico