Which command verifies that graceful Routing Engine switchover (GRES) is operational?

A.
show system switchover on the master RE

B.
show system switchover on the backup RE

C.
show task replication on the master RE

D.
show task replication on the backup RE

Explanation:
Verify That Graceful Routing Engine Switchover and Nonstop Active Routing Are Configured

Before you begin a unified ISSU, ensure that graceful Routing Engine switchover and nonstop active routing are configured on your router.

1. To verify graceful Routing Engine switchover is configured, on the backup Routing Engine (re1) issue the show system switchover command. The output should be similar to the following example. The Graceful switchover field state must be On.
{backup}

user@host> show system switchover
2. Graceful switchover: On
3. Configuration database: Ready
4. Kernel database: Ready
5. Peer state: Steady State
6. To verify nonstop active routing is configured, on the master Routing Engine (re0) issue the show task replication command. The output should be similar to the following example.
7. {master}
user@host> show task replication
Stateful Replication: Enabled
RE mode: Master

Protocol Synchronization Status
OSPF Complete
IS-IS Complete

If graceful Routing Engine switchover and nonstop active routing are not configured, complete the following steps:

1. On the master Routing Engine (re0), enable graceful Routing Engine switchover. Include the graceful-switchover statement at the [edit chassis redundancy] hierarchy level.
2. On the master Routing Engine, enable nonstop active routing. Include the commit synchronize statement at the [edit system] hierarchy level and the nonstop-routing statement at the [edit routing-options] hierarchy level.
3. On the master Router Engine, issue the commit command.
The system provides the following confirmation that the master and backup Routing Engines are synchronized:

re0:
configuration check succeeds
re1:
commit complete
re0:
commit complete