He was given a severe warning for coming late.

Answer: Option B

Rigorous : extremely thorough and careful.
Stern : (of a person or their manner) serious and unrelenting, especially in the assertion of authority and exercise of discipline.
Harsh : unpleasantly rough or jarring to the senses.
Strict : demanding that rules concerning behaviour are obeyed and observed.
Severe : (of a person) formal and unsmiling.

Synonym of Severe is Stern