Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : MPP can be zero or negative but not APP.
Reason (R) : Because, APP is the ratio between TPP and units of variable factor (which is always positive) while MPP is change in TPP (owing to an additional unit of the variable factor) which can be zero or negative.
In light of the above statements, choose the correct answer from the options given below: