A 4-bit ripple counter consists of flip-flops, which each have a propagation delay from clock to Q output of 15 ns. For the counter to recycle from 1111 to 0000, it takes a total of ________.

A 4-bit ripple counter consists of flip-flops, which each have a propa

1.	A 4-bit ripple counter consists of flip-flops, which each have a propagation delay from clock to Q output of 15 ns. For the counter to recycle from 1111 to 0000, it takes a total of ________.
A.	15 ns
B.	30 ns
C.	45 ns
D.	60 ns
Answer» E.