Single correct option
The number of relations on the set that are both reflexive and symmetric is
- A.
- B.
- C.
- D.
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Answer: (A)
A reflexive relation must contain all four pairs . A symmetric relation is fixed by deciding, independently, whether each unordered pair with is included. There are such pairs, each included or not, so the count is . The values (symmetric only, ) and (reflexive only, ) count relations with just one of the two properties.
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