Which ones of following operations invert a single-bit input X? Choose all that apply

a) X = X xor 0

b) X = X xor 1

c) X = X nand 0

d) X = X nand 1

e) X = X nor 0

f) X = X nor 1

g) X = X xnor 0

h) X = X xnor 1

i) none of above