Question

a single organ system

1. what do groups of similar cells form in a multicellular organism?

systems
organs
tissues
bones

Explanation:

In a multicellular organism, cells are the basic unit. Groups of similar cells that work together to perform a specific function form tissues. Systems are made up of multiple organs, organs are composed of different tissues, and bones are a type of organ (involving bone tissue, connective tissue etc.). So the key is the definition of tissue as a group of similar cells.

Answer:

Tissues