Oxalic acid in leafy vegetables reduce the bio-availability of

Answer: Option A

Oxalic acid in leafy vegetables reduces the bio-availability of Calcium.
Oxalic acid can reduce mineral absorption. One of the main health concerns about oxalate is that it can bind to minerals in the gut and prevent the body from absorbing them.
For example, a leafy vegetable like spinach is high in calcium and oxalate, which prevents a lot of the calcium from being absorbed into the body.