earlier to IEEE 758 representation, floating numbers couldn't differentiate -0 and +0. So, they come up with IEEE 758 floating poing representation in 32 bit and 64 bit and they marked +0 and -0 representation special that's all I read somewhere, don't know exact history.

sir why not A??
this 32 bit ieee representation also correspond to normalize 2^(-127)
using bias=(2^(8-1))-1 value= (-1)^0 * 1.(23 0's) * 2^(0-bias)=1*2^(-127)
1 implicit here and not stored. @arjun sir plz reply

srry got the point, we can't take all zero in exponent part in case of ieee 754 single precision, min value that can be stored is 2^(-126), which in case of when exponent field contain 1 in LSB position and all zero in mantissa part, so given format reserved for special value/ thanks