Why Are Tier-2 Costs Called 'Hidden' Environmental Costs

Why are Tier-2 costs called 'hidden' environmental costs?

A) They are hidden in the accounts so that stakeholders are unaware of the potential environmental risks of the firm.
B) They tend to be included in other accounts such as overhead and therefore are not easily identifiable.
C) They are uncertain because it is not possible to show them in a separate account.
D) Environmental costs cannot be estimated with any degree of certainty.