Question

What are tissues made of?

A. Groups of cells
B. Groups of systems
C. Groups of reflexes
D. Groups of organs

Answer 1

Tissues are made of A. Groups of cells. The levels of organization are:
1. Cell (smallest)
2. Tissue
3. Organ
4. Organ System
5. Organism (largest)
Each thing following another is made up of the things before it. For example, if you look at an organism, you know that an organism is made up of organ systems, which are made up of organs, which are made out of tissue, which is made from cells. I hope this helps.

Answer 2

A. Group of cells

Cells - Tissue - Organ ...

If you want to know more - look for "Biological Organisation"