In a 4 bit ripple counter using flip flops with tpd = 40 ns, the maximum frequency can be-A-1.25 MHzB-3.25 MHzC-6.25 MHzD-12.5 MHz-C-6.25 MHz

C 6.25 MHz Total time delay = 40 x 4 = 160 x 100 9s. Hence .