You decide to create a cluster which runs HDFS in High Availability mode with automatic failover,
using Quorum-based Storage. What is the purpose of ZooKeeper in such a configuration? 

It manages the Edits file, which is a log changes to the HDFS filesystem. 

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 

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

Clients connect to ZoneKeeper to determine which NameNode is Active