Which of the following has the same expressive power with regard to relational query language?
(a) Relational algebra and Domain relational calculus
(b) Relational algebra and Tuple relational calculus
(c) Relational algebra and Domain relational calculus restricted to safe expression
(d) Relational algebra and Tuple relational calculus restricted to safe expression
1
(a) and (b) only
2
(c) and (d) only
3
(a) and (c) only
4
(b) and (d) only