4-bit 2's complement range: −8 to +7. Overflow happens when two numbers of the same sign give a result of the opposite sign.

• (A) 1111 + 1101 = (−1) + (−3) = −4 → 1100. No overflow.
• (B) 0110 + 0110 = 6 + 6 = 12 → 1100, which reads as −4. Overflow.
• (C) 1101 + 0101 = −3 + 5 = 2. No overflow (signs differ).
• (D) 0101 + 1011 = 5 + (−5) = 0. No overflow.

Answer: (B)