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Let \(X = \{1, 2, 3, 4, 5, 6, 7\}\) . Let \(R = \{(1, 1), (1, 2), (1, 3), (5, 6), (6, 7), (7, 5)\}\) be a relation on X. Then the relation R will become reflexive if we include the pairs

  • A.(2,7),(3,3),(5,5),(6,6) and (7,7)
  • B.(2,2),(4,3),(5,5),(6,6) and (7,7)
  • C.(2,2),(3,3),(5,5),(6,6) and (7,6)
  • D.(2,2),(3,3),(5,5) and (7,7)
  • E.(2,2),(3,3),(4,4),(5,5),(6,6) and (7,7)

Answer: E

R becomes reflexive on adding (2,2), (3,3), (4,4), (5,5), (6,6) and (7,7).

A relation on X is reflexive when \((x, x) \in R\) for every \(x \in X\). R already contains (1,1) but none of (2,2) to (7,7), so all six must be added.

The other options each fail somewhere: one swaps (2,2) for (2,7), one replaces (4,4) with (4,3), one has (7,6) instead of (7,7), and one leaves out (4,4) and (6,6). Pairs such as (2,7) or (4,3) do not help, since only pairs of the form \((x, x)\) count.

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