resolve the apparent discrepancy

Premise 1 - One way kidney stones can form is when urine in the kidneys is overly concentrated with calcium or oxalate.
Premise 2 - Reducing dietary calcium leads to decrease the likelihood that calcium will concentrate and form additional stones.
Paradox - For many people the chances of recurrence are decreased by increasing calcium intake.

Logic - we are trying to find an alternate cause which might lead to the paradox. So, maybe some external factor is mitigating the effect of increased calcium intake.

A) Laboratory studies on animals with kidney stones reveal that they rarely get additional stones once calcium supplements are added to the diet. Out of scope

B) Increasing dietary oxalate while reducing dietary calcium does not reduce the chances of kidney stone recurrence. - Maybe, but the paradox does not talk about Increasing dietary oxalate. - Out of scope

C) Kidney stone development is sometimes the result of an inherited disorder that can result in excessive production of calcium and oxalate. - Talks about causes of kidney stone -Out of scope

D) Increasing calcium intake increases the amount of calcium eliminated through the intestines, which decreases the amount to be filtered by the kidneys. - Looks ok, the calcium reaching the kidneys is already in decreased amounts, hence the chances of kidney stone development are low.

E) Some kidney stones are composed of uric acid rather than a combination of calcium and oxalate. - out of scope

Will go with D

Answer D seems to be logical one out of other answer choices