The correct answer is C. Equal.
A consumer consuming two goods will be in equilibrium when the marginal utilities from both goods are equal. This is because the consumer will be getting the same amount of satisfaction from each good, and will not be able to increase their satisfaction by consuming more of one good and less of the other.
Option A is incorrect because the marginal utility from a good can never be zero. This is because the consumer will always get some satisfaction from consuming a good, even if they consume a very small amount of it.
Option B is incorrect because the marginal utility from a good can never be maximum possible positive. This is because the consumer will eventually reach a point where they get diminishing marginal utility from consuming more of a good. This means that the additional satisfaction they get from consuming more of the good will decrease.
Option D is incorrect because the consumer will only be in equilibrium when the marginal utilities from both goods are equal.