M Mr. Dubey 🎓 Coach ⭐ 102.92K Points 📊 Hadoop Q. What is a heartbeat in Hadoop? (A) Signal sent from NameNode to DataNode (B) Health check signal sent from DataNode to NameNode (C) Data packet from reducer (D) Job status update 👁️ Show Answer 💬 Discuss 🔗 Share ⚡Menu ✅ Correct Answer: (B) Health check signal sent from DataNode to NameNode Explanation: DataNodes send heartbeats to NameNode regularly to confirm they are alive.