Correct Answer : _id
Explanation : ID value value must be unique in the collection, is immutable, and may be of any type other than an array.
Correct Answer : sh.disableBalancing()
Explanation : sh.disableBalancing() does not affect balancing of other collections in a sharded cluster.
Correct Answer : sh.getBalancerHost()
Explanation : sh.enableSharding() enables sharding on a specific database.
Correct Answer : sh.getBalancerState()
Explanation : sh.getBalancerState() returns true when the balancer is enabled and false if the balancer is disabled.