Why should the percentage of allowed weed or other crop seed be under 2 percent? O These other plants will compete with the desired plant for attention, rain, and desiccants.
O These other plants will compete with the desired plant for light, space, and nutrients.
O These other plants will compete with the desired plant for shelf space, threshing, and roguing.
O These other plants will compete with the desired plant for soil, worms, and warmth.

The correct answer is lactic acid.

Explanation:

Lactic acid comes from the breakdown of glucose when there is no oxygen present (glycolytic metabolism), that is, in an anaerobic exercise such as lifting weights or running at high speed, like our student in the question, where there is a lot of intensity and short duration. Under normal conditions that lactic acid and when we are trained it is reused and there is no problem.  

But when we continue with intensity an exercise, lactic acid will begin to accumulate by not giving the body time to remove it. This causes high concentration of lactic acid in the muscle fibers, which has two important consequences:

1. The enzymes responsible for breaking the glucose molecule to obtain energy are inhibited, so the energy grind of this path is cut off and as we know, if there is no energy, there is no movement.

2. It prevents calcium from joining the muscle fibers and consequently from contraction.  Therefore, when there is a lot of lactic acid in the body, we have neither energy nor capacity to contract the muscles, this is nothing but fatigue and the best we can do is stop the exercise or activity. That's our recommendation to our student after running 2 km as fast as she could.