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Que. Let r be a relation instance with schema R = (A, B, C, D). We define r1 = ΠA, B, C (r) and r2 = ΠA.D (r). Let s = r1 * r2 where * denotes natural join. Given that the decomposition of r into r1 and r2 is lossy, which one of the following is TRUE?
a. s ⊂ r
b. r ∪ s
c. r ⊂ s
d. r * s = s
Answer:r ⊂ s
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