The correct answer is C. harsh.
A harsh warning is one that is severe or severe. It is a warning that is likely to make the person who receives it feel very bad or guilty.
A rigorous warning is one that is strict or demanding. It is a warning that is likely to make the person who receives it feel like they have to do something very difficult or challenging.
A stern warning is one that is serious or severe. It is a warning that is likely to make the person who receives it feel like they are in trouble.
A strict warning is one that is demanding or firm. It is a warning that is likely to make the person who receives it feel like they have to follow the rules very carefully.
In this case, the person was given a harsh warning for coming late. This means that the warning was likely to make the person feel very bad or guilty.