Why is precambrian time about 88% of geologic time not divided into smaller units based on the fossil record?

The fossil record of precambrian time contains few fossils so there is not any reason to subdivide it.

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.

Answer (d) may increase or decrease porosity through dissolution or deposition;