You perform the following operation in the shell: db.foo.insert( { } ); What gets inserted?

Which of the following collections stores authentication credentials in MongoDB?

Given a replica set with five data-bearing members, suppose the primary goes down with operations in its oplog that have been copied from the primary to only one secondary. Assuming no other problems occur, which of the following describes what is most likely to happen?

In a sharded replica set environment, the w Option provides ability for write concern and j Option provides ability for the data to be written on disk journal. Consider that we have a seven member replica set and we want to assure that the writes are committed to journal. What should be the value of j?

Consider the following example document:
{
"_id": Objectld("5360c0a0a655a60674680bbe"),
"user"
"login": "irOn"
"description": "Made of steel"
"date": ISODate("2014-04-30T09:16:45.836Z"),
}
>
and index creation command:
db.users.createlndex( { "user.login": 1, "user.date": -1 }, "mylndex" ) When performing the following query:
db.users.find( { "user.login": /Air.*/ },
{ "user":1, "_id":0 > ).sort( { "user.date":1 > )
which of the following statements correctly describe how MongoDB will handle the query? Check all that apply.