Hello Micaela,

Yes, this is a tricky question! For the MCAT you do not want to ponder too long on always rationalizing why certain answers are wrong, you want to develop the skill of picking the BEST possible answer.

Although ADH will increase water resorption with aquaporins, but it will also increase systemic vascular constriction resulting in an increase in the blood pressure which will increase the flow of fluid through the kidney system and decrease, rather than increase, water reabsorption or ability to concentrate, so these answer choices are incorrect. If GFR is moving really fast, the channels and aquaporins will not have sufficient time to do their work. This would be an example of choosing the best answer and the course of action that would occur firstly.

Do not stress too much about the specific details, just really try to work on the skill of MCAT taking.

Goodluck!