How many flip-flops are required to build a binary counter that counts from 0 to 4095? 

The correct option is 10.

Concept:

Counters:

• It is a sequential logic circuit that has a clock input signal and a group of output signals
• It represents an integer "counts" value.
• Internally, counters use flip-flops to represent the current counts and to retain the counts between clocks.
• N values can be counted with n number of flip flops. its relation is given by-

           \(2^n\geq N\)

where, N = number of counts

          n = number of flip flops

Calculation-

Given- N= 4095

 \(2^n\geq 4095\)

 \(n=12\)

 Hence total of 12 flip flops are required to count from 0 to 4095.