Identify the chirality center (sometimes called chiral atom) or centers in each compound. if the molecule does not contain a chirality center, do not highlight any of its atoms. select an atom by clicking on it. selected atoms will be highlighted green.

Chiral Carbons are those carbons which are attached to four different atoms or groups. Below are the four structure, Among these structures, 

Structure C has no chiral carbon because the carbon to which methyl group and hydrogen atom attached is further attached to groups of same environment.

Structure A has one chiral center (highlighted RED).

Structure B has three chiral centers.

Structure D has two chiral centers.

Below are  the structures,

Less stable  hope this