Why are some organisms muticellular

Multicellular organisms need specialised systems

The cells get oxygen and nutrients from this extracellular fluid and release waste products into it. Humans and other complex organisms have specialised systems that maintain the internal environment, keeping it steady and able to provide for the needs of the cells.

Explanation:

the rocks are classified by the geological process they are formed by. the three main groups of rocks are igneous, metamorphic, and sedimentary. minerals are not they are classified under the chemical classes they are in. these groups include silicates, sulfates and carbonates.