Step 1: Understand the logic.
The original statement is "He is poor but happy". The negation of this statement is formed by negating the individual components using De Morgan's laws.
Step 2: Apply De Morgan's law.
The negation of "He is poor but happy" is "He is not poor or not happy," which is option (B).
Step 3: Conclusion.
Thus, the negation of the statement is "He is not poor or not happy," corresponding to option (B).