In the Section "Investigating Life: in (Extremely)Cold Blood",why Would Ice

In the section "Investigating Life: In (Extremely) Cold Blood",why would ice fish lose their alpha and beta globin genes through mutation?

A) If hemoglobin was not necessary there was no selective pressure to keep mutations from accumulating.
B) The fish wanted to stop producing red blood cells,so they mutated the globin genes.
C) Fish with red blood cells were more visible to predators and were eaten.
D) Mistakes in DNA replication are more likely to occur at colder temperatures.
E) Fish living in the cold cannot obtain enough iron to make hemoglobin.