Which command returns the remaining time to live of a key in seconds?

1. A EXPIRE key
2. ✓ B TTL key (correct answer)
3. C PERSIST key
4. D OBJECT IDLETIME key

Shortcut: TTL returns the remaining lifetime in seconds, -1 if the key has no expiry, and -2 if the key does not exist. PTTL gives the same in milliseconds.