Which of the following has the largest number of unpaired electrons?

a. [CrCl₆]⁴⁻
b. [Ni(CN)₄]²⁻ (square planar)
c. Tetrachlorocobalt (II) ion (tetrahedral)
d. A low spin octahedral complex of Fe³⁺
e. More than one of the listed answer choices has the same largest number of unpaired electrons