Cells are organized into tissues, and tissues form organs, and different tissues are in turn grouped together to form functional units, called organs. Given these facts, cells are organized into tissues to what among the following options:
- Veins and arteries.
 - allow growth
 - move blood
 - become functional units
 - by keeping them warm
 - organize hair
 - protect plants
 - change body color


 

    become functional units     