Answer:
The correct answer is letter "D": Private negotiations.
Step-by-step explanation:
Environmental efficiency through markets is in charge of promoting the creation of more goods and services without the need for exploiting more resources or increasing pollution. Its purpose is to take sustainability towards economic efficiency considering ecological awareness.
In that case, private negotiations could boost environmental efficiency since firms could create partnerships among them to contribute to each other in their production process to avoid the use of more natural resources.