Multiple choice:The five basic relational algebra operations are ().

The five basic relational algebra operations are ()@[ A](2)
A. ∪ － × σ π
B. ∪ － σ π
C. ∪ ∩ × σ π
D. ∪ ∩ σ π




A.∪ － × σ π
B.∪ － σ π
C.∪ ∩ × σ π
D.∪ ∩ σ π


answer：A