Answer: D. All of the above are correct.
Explanation:
The marginal rate of technical substitution (MRTS) refers to the economic theory which explains the rate at which a particular factor of production must reduce in order for the same level of productivity to be maintained when there's another production factor which is increased.
When the capital is plotted on the vertical axis and labor is plotted along the horizontal axis, then the marginal rate of technical substitution of labor for capital along a convex isoquant will reduce as more and more labor is used. Also, the MRTS equals the negative of the slope of the isoquant and equals the marginal product of labor divided by the marginal product of capital that's MRTSL,K=-MPL/MPK
Therefore, the correct option is All of the above.