Read the following and answer the question based on it.

Proteins are used by the body for energy, metabolism, gene growth and maintenance. 10 to 35 percent of the daily calorie intake should ideally consist of proteins. They are found in all cells of the body. Hair and nail are made up of a protein called keratin, having sulphur bonds. Curlier hair has more sulphur links. Too much intake of proteins can sometimes lead to body weight.
Proteins ............

In the first two sentences passage describes that :

Proteins are used by the body for energy, metabolism, gene growth and maintenance. 10 to 35 percent of the daily calorie intake should ideally consist of proteins.

Means proteins are essential factors for body maintenance.

As well as it is necessary for hair, nail.

But in last para it says that execive protien leads to body weight.

So,Protiens are necessary element for human body but it must consume in limit.

So,B is correct choice.