Option D has the highest concentration of lactic acid in the student's muscle tissue.
We can arrive at this answer because:
As we can see in the information presented above, option D shows the performance of flexions with more intensity and for a longer period, which justifies a greater accumulation of lactic acid in the muscle.
It is important to remember that the accumulation of lactic acid in the muscle is a negative situation and that it can cause muscle pain and fatigue.
More information on lactic fermentation at the link:
https://brainly.com/question/13769502