17) C

1 – Since ADH is a hormone, it has to travel in the bloodstream. So this is correct. 

2 – ADH causes water to be reabsorbed into the bloodstream from the kidney. Hence, urine produced would be concentrated and not dilute. 

3 – Same concept. Increased ADH will cause increase in concentrated urine and not dilute urine. 

4 – This is correct. ADH is released by the pituitary gland to reabsorb water from the kidney to prevent dehydration. If ADH is reduced, dehydration can occur. 

The answer is C.