What is a unifying feature of all animals, but is not seen outside of the animal kingdom?

i'd say that the moon rock is about 2.2 billion years old.

the sphincter muscles at the end of the digestive tract is the anus.

the eggs of the insects should be the first thing collected at the scene.

false

1. efficient use of space

2. elimination of groundwater contamination

3. energy generation

4. lower carbon footprint