Compact bone contains cylinders of calcified bone called . These cylinders consist of 4 to 20 concentric rings of bone known as . g

Kelly ran electricity though a sample of water using electrolysis. the water changed into two gases, x and y. it was not possible to break down the gases x and y into simpler particles.

Aplant may open end close its stomata to prevent excess water loss and maintain

Archaebacteria use for movement. celia flagella pili cell walls