You decide to create a cluster which runs HDFS in High Availability mode with automatic...

It only keeps track of which NameNode is Active at any given time

It monitors an NFS mount point and reports if the mount point disappears

It both keeps track of which NameNode is Active at any given time, and manages the Edits file. Which is a log of changes to the HDFS filesystem

If only manages the Edits file, which is log of changes to the HDFS filesystem

Clients connect to ZooKeeper to determine which NameNode is Active