Answer:
A. A Building artificial reefs and limiting fishing activity
Step-by-step explanation:
Building artificial reefs will limit the overfishing and also limit decrease in number of living in the marine ecosystem.
An artificial reef is a man made marine structure with no bottom which is used to block the passage of unwanted artificial things in the marine ecosystem such as trawling nets and ships. So, artificial reef will block the equipment used by fishing industry, which limit their fishing activity and help the marine life to grow.
Hence, the correct option is A.