Let a be an m × n matrix. which of the following statements must be true regarding the nullity (dimension of the null space) of a?

i) the nullity of a is the same as the number of nonzero rows in a row echelon form of a.
ii) the nullity of a is the same as the dimension of the column space of a.
iii) the nullity of a is the same as the nullity of a^t

a. none of the statements are correct.
b. i) and ii) only
c. i) and iii) only
d. ii) and iii) only
e. all three statements are correct.