What does the totalKeysExamined field returned by the explain method indicate?

Which features of relational database management systems were deliberately omitted in MongoDB and help us to obtain horizontal scalability? Check all that apply.

What is the use of mongodump and mongorestore tools?

Which of the following is true of the mechanics of replication in MongoDB? Check all that apply.

Below is a sample document in a given collection test.
{ a : 5, b : 3, c: 2, d : 1 >
Given a compound index { a: 1, b:l, c:l, d:l}, Which of the below query will not use in-memory sorting? Select all valid.