Answer:
Option B, implementation of a cap and dividend policy
Step-by-step explanation:
A milestone represent a significant stage or event in any project or program. Among all the given options, option C “implementation of a cap and dividend policy” has not yet been achieved till date today and hence it can be a possible milestone. While “water pollution policy” has already been declared and hence it would have been a milestone in past. Like wise both the “mandatory environmental assessments” and “environmental impact statements” have been done since ages to asses the impact on an activity on environment.