Question : What is primary key. Choose from the options given below - 

Option 1: A Primary key is a field or a combination of fields that can uniquely identify a row/tuple in a table/relation.

Option 2: A Primary key in table/relation is any non-primary key field which also stores unique values for each row just like a primary-key does. But only one key is designated as primary key. So unique refers to a unique non-key field of a table.

Option 3: A Primary key is a field of a table which is the primary key of another table through a foreign key a relationship is established between two tables.

Option 4: None of the above