Which of the following cells lacks mitochondria?

a. neutrophil
b. platelets
c. basophils
d. erythrocytes

I just need some assistance and assurance that my answer is reasonable.
I'm thinking that the answer is d. erythrocyte because it is not a true cell. I know that the leukocytes are true cells which include the neutrophil and basophil. Platelets are just fragments of megakaryocytes.