In relational algebra, the five basic operations are:
A.
∪ 、-、 × 、 σ 、 π
B.
∪、 -、 σ 、 π 、 ÷
C.
∪、 ∩ 、 × 、 σ 、 π
D.
∪、 ∩ 、 σ 、 π 、-
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