Step 1: Concept Distances in consecutive seconds are equal only if the body reaches its maximum height at the end of the first of those two seconds.
Step 2: Meaning This means the velocity becomes zero exactly at $t=5$ seconds.
Step 3: Analysis Using $v = u - gt$: $0 = u - (9.8 \times 5)$.
Step 4: Conclusion $u = 49~m/s$.
Final Answer: (B)