The MP of a factor

The Marginal Product (MP) of a factor like labour in an initial stage shows positive growth, but in a meanwhile production, it can be zero means no contribution to production.

If we transfer some labour to another work, the final product can not be affected.

If we can not remove some workforce, it is a waste of input, and MP could be negative.

This situation is generally seen in the agricultural sector

Hence, the correct answer is C. Can be positive, negative or zero.