The relational algebra expression equivalent to the tuple calculus expression
$\{t\mid t \in r \land (t[A]=10 \land t[B]=20)\}$ is
Option C
t ia table have two attribute A,B
$({t∣t∈r∧(t[A]=10∧t[B]=20)}$ MEANS one of the tuple of table t value of A=10 and B=20
here r is table with attribute A,B
$σ(A=10)(r)∩σ(B=20)(r)$ means one of the tuple of table r value of A=10 and B=20
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