Question

In a 4-bit ripple carry adder, the worst-case delay occurs when _______.

• A. All input bits are 0
• B. A carry propagates through all full adders
• C. No carry is generated
• D. The sum exceeds 15

Hint:

In a ripple carry adder, the speed is limited by the propagation of carries, so minimizing carry propagation is key to improving speed.

Answer 1

The Correct Option is B

In a ripple carry adder, the carry bit must propagate through each full adder in sequence. The worst-case delay happens when the carry bit propagates through all full adders, as it takes the longest time for the carry to be computed. 
Therefore, the correct answer is option (2).