Among the characteristics unique to animals is
a. gastrulation c. sexual reproduction
b. multicellularity. d. flagellated sperm

a.gastrulation is the correct answer.

Explanation:

The characteristics unique to animals is gastrulation

Gastrulation is a stage early in the embryonic growth in most of the animals, through which simple layered blastula is rearranged into a multi-layered structure called gastrula.

gastrulation results in the formation of three germ layers

The embryonic tissue layers are developed and arranged in their proper places during the gastrulation process.

good thing- during decomposition the organic molecules in organic matter are broken down into simpler organic molecules that require further decomposition or into mineralised nutrients

bad thing- it can be harmful in crop productivity

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.