A characteristic unique to animals is?

Question

A heterotrophic nutrition.
B sexual reproduction.
C gastrulation.
D fagellated sperm.
E multicellularit

Answer 1

I would say it is C
It is not A b/c fungi can be considered heterotrophic
It is not B b/c plants have sexual reproduction
It is not E b/c plants and fungi can be multicellular
I do not know if only animals have flagellated sperm but I am pretty sure only animals have gastrulation.