The Spectral Types for Each of Five Stars Are Given $\alpha$

The spectral types for each of five stars are given. Which star in would have the greatest surface temperature?

A) ( $\alpha$ For; F8)
B) (o Cet; M7)
C) 35 Ari; B3
D) ( $\gamma$ Tri; A0)
E) ( Per; O7)