what is mesosphere?

The chemicals present in mesosphere are

Consider the following statements : (i) Zirconium - alizarins due is used for testing fluoride ions is water (ii) Ozone layer is present in mesosphere (iii) the poisonous gas present in the exhaust fumes of automobiles is Co (iv) Taj Mahal is affected by CO_(2) gas The correct statement are

Transitional layer between stratosphere and mesosphere is

Separating the mesosphere from the stratosphere is transition zone called

What is an ionosphere? What does it contain ?