If Neutrinos Have Mass but Do Not Interact Much with Normal

Multiple Choice

If neutrinos have mass but do not interact much with normal matter,why can't they be the dominant form of dark matter in the universe?

A) Structure formation would have started with large objects fragmenting into smaller objects.
B) Structure formation would have started with small objects merging to form larger objects.
C) Neutrinos would decay over time and disappear,causing galaxies to fall apart.
D) Neutrinos would not gravitationally lens background galaxies.