Fact 1: Cells are organized into tissues, and tissues form organs.

Fact 2: Examples of animal organs are kidneys and hearts.

Given the two facts above, answer the question "what do tissues form?" with the following options: 
- the skin
 - ferns
 - clouds
 - density
 - alveoli
 - kidneys
 - h2o
 - perennials


 

      kidneys   