Answer:
The four C's are Carat, color , cut and clarity. Whenever you purchase any diamond always keep these 4 C's in mind,
Carat is related to the weight of the diamond.
Cut is related to the shape and design of the diamond
Color is related to the color, color I mean be careful , science has found ways to add color to a diamond
Clarity is related to genuineness of the diamond. You can use a diamond Loupe as tool to measure a diamonds clarity.