On (A={1,2,3,4,5}), (aRb) if and only if the squares of (a) and (b) leave the same remainder on division by (5). Which is the equivalence class of (2)?

Correct answer: ({2,3})

Step 1: (2^2=4), so the square of (2) leaves remainder (4) modulo (5). Step 2: (3^2=9) also leaves remainder (4) modulo (5). Step 3: The squares of (1) and (4) leave remainder (1), so the class of (2) is ({2,3}).