Answer is B).
For DAC (Digital to analog convertor) ===> Every input has a weight and the output voltage is the sum of the weights of 1's in the input.
If the maximum output voltage of a DAC is V volts and if the resolution is R bits, then,
Weight of least significant bit is ==> V/2R - 1
Weight of second least significant bit is ==> 2V/2R - 1
Weight of third least significant bit is ==> 4V/2R - 1
Weight of fourth least significant bit is ==> 8V/2R - 1 , and so on................
Weight of Most significant bit is ==> (2R - 1 ) V/2R - 1