Assertion : The electrical conductivity of earth?s atmosphere decrease with altitude. Reason : The high energy particles (i.e. g-rays and cosmic rays) coming from outer space and entering our earth?s atmosphere causes ionisation of the atoms of the gases present there and the pressure of gases decreases with increase in altitude.

• A.    If both assertion and reason are true and the reason is the correct explanation of the assertion.
• B.    If both assertion and reason are true but reason is not the correct explanation of the assertion.
• C.    If assertion is true but reason is false.
• D.    If the assertion and reason both are false.
• E.    If assertion is false but reason is true.