What distinguishes ambient water quality criteria from enforceable water quality standards, and how do they relate to permits?

• A. Standards are guideline values; ambient criteria are legally enforceable thresholds; permits are designed to enforce those standards.
• B. Criteria are guideline values; standards are legally enforceable thresholds; permits set limits to meet standards and protect designated uses.
• C. Ambient criteria and enforceable standards are identical in effect and are both used to set emission allowances directly.
• D. Criteria specify water uses only, while standards specify numeric limits for all pollutants.

Answer: (B)