What is vertex coloring of a graph?

A. A condition where any two vertices having a common edge should not have same color

B. A condition where any two vertices having a common edge should always have same color

C. A condition where all vertices should have a different color

D. A condition where all vertices should have same color

What is a chromatic number?

A. The maximum number of colors required for proper edge coloring of graph

B. The maximum number of colors required for proper vertex coloring of graph

C. The minimum number of colors required for proper vertex coloring of graph

D. The minimum number of colors required for proper edge coloring of graph