A : An exact number has infinite number of significant digits. R :
A number, which is not a measured value has infinite number of significant digits.

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion.
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then.
C. If Assertion is true statement but Reason is false, then.
D. If both Assertion and Reason are false statements, then.