A person of good understanding knowledge and reasoning power

Answer: Option B

One word substitution is Intellectual.

Expert: a person who is very knowledgeable about or skilful in a particular area.
Intellectual: Intelligent; knowledgeable.
Snob: a person with an exaggerated respect for high social position or wealth who seeks to associate with social superiors and looks down on those regarded as socially inferior.
Literate: able to read and write.