According to the "Out of Africa" Theory, What Led to the Disappearance

According to the "out of Africa" theory, what led to the disappearance of Neandertals?

A) Modern Homo sapiens evolved first in Africa and then migrated to other areas, eventually replacing and assimilating with Neandertals.
B) Neandertals were unable to interbreed with Homo erectus after migrating out of Africa.
C) Modern Homo sapiens directly evolved from Neandertals once the Neandertals left Africa.
D) Modern Homo sapiens displaced Homo erectus in Africa, who in turn displaced Neandertals in Europe.