Which is a line of dialogue?
"i have taken all of the stress i can stand."
i could not understand how we had gotten to this point.
"the group took all results into consideration," the study reported.
i thought we had gotten beyond this issue the last time we talked.

Your first option, "I have taken all the stress I can stand.", is a line of dialogue.

Dialogue is speaking/talking. The second and last options cannot be examples of dialogue because they are not being spoken (you can tell by the lack of quotation marks).The third option is also incorrect because it is what is written, as it says "the study reported" (the study does not speak). Therefore, the first option is correct.