When emissions are measured on the horizontal axis, the marginal cost

When emissions are measured on the horizontal axis, the marginal cost of abating emissions is

A) downward-sloping because emissions become more and more easy to eliminate once the firm makes the initial commitment to do so.
B) downward-sloping because a high level of emissions is cheap to attain, and a low level of emissions is expensive to attain.
C) upward-sloping because emissions become more and more easy to eliminate once the firm makes the initial commitment to do so.
D) upward-sloping because a high level of emissions is cheap to attain, and a low level of emissions is expensive to attain.
E) horizontal because the technology to remove emissions is assumed constant.

ANSWER

B