Assertion : A potentiometer of longer length is used for accurate measurement. Reason : The potential gradient for a potentiometer of longer length with a given source of e.m.f. becomes small.

• 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.