What is join operation in Structure Query Language (SQL)?

1. AJoin is an operation used to select group rows of a table that contains the same values in a specific column.
2. BJoin is an operation which is used to combine two different data keys.
3. CJoin is an operation used to combine rows from two or more tables based on one or more common fields between them.
4. DJoin is an operation which work on a single row of a table and return a single value.