Answer : C) The smallest number is represented by all zeros.
In computer system, a floating-point number is represented as S E M, i.e. using Sign bit, Exponent bits and Mantissa bits.
The exponent can be a positive as well as a negative number. So to represent negative number we can use $1's$ complement or $2's$ complement. Better choice would be $2's$ complement.
If we use $2's$ complement system to represent exponent, then problem will arise while comparing $2$ floating point numbers. For example, if exponent of the $2$ numbers are negative then for comparing we will have to convert them into positive number.
So, to avoid this extra work, excess-N code is used so that all exponent can be represented in positive numbers, starting with $0$.