Correct option is B
The correct one-word for the given group of words is (b) callous.
Callous means showing or having an insensitive and cruel disregard for others; emotionally hardened. (निर्दयी, कठोर)
Example: The company was callous in firing employees without warning.
Meanings of the given other options:
· (a) Merciful – Showing compassion or forgiveness. (दयालु)
· (c) Tender – Gentle and caring in behaviour. (कोमल, संवेदनशील)
· (d) Compassionate – Feeling or showing sympathy and concern for others. (करुणामय)