The iron in breakfast cereal is absorbed more readily when consumed with a glass of vitamin c-rich orange juice.

This question is obviously incomplete. However, it is true that vitamin C aids in the absorption of iron. There are different forms of iron in the diet, with some forms more readily absorbed than others. Soluble haem iron found in meat is the most readily absorbed iron. Non-haem iron is commonly found in the ferric form, and is not as readily absorbed. However, vitamin C can aid in the reduction of the ferric form to a ferrous form which is more readily absorbed.