What action does ⋈ operator perform in relational algebra

[answerhappygod]

a) Output specified attributes from all rows of the input relation and remove duplicate tuples from the output
b) Outputs pairs of rows from the two input relations that have the same value on all attributes that have the same name
c) Output all pairs of rows from the two input relations (regardless of whether or not they have the same values on common attributes)
d) Return rows of the input relation that satisfy the predicate