Answer is Ca which is a metal.
Explanation: Milk is composed of many elements such as Calcium (Ca), Magnesium(Mg), Phosphorus(P), Potassium (K), Zinc(Zn) ans Selenium(Se). The major component present is Ca.
Calcium present helps in the formation of bones and teeth and maintaining it to keep healthy.
Elements which can loose electrons easily to obtain a stable configuration is called as a metal.
Calcium is a metal as it can easily loose 2 electrons to obtain a stable configuration.
[tex]Ca\rightarrow Ca^{2+} +2e^-[/tex]
