Veznici i poveznice rečenica

Read the text and choose the option (A-F) that best completes gap (16).

Ghost nets

Fishing nets used to be made from rope. But since the 1960s, they are made from nylon, (0) a material that is much stronger and cheaper. Nylon is plastic and it does not break down. That means that fishing nets lost in the ocean, called ghost nets, (16) ____. Because of this, hundreds of millions of marine animals are killed or injured every year.

Ghost nets injure and kill marine animals and fish that become trapped. There is plenty of life around abandoned fishing nets, (17) ____. Sea turtles look for floating objects to hide under them (18) ____. But turtles do not know that ghost nets are not safe for them and they get caught.

The problem of ghost nets has been known for years but (19) ____. Even though one of them, Fishing Ltd, did mention the problem, there were no reports on it. Moreover, it's impossible to identify which ship a ghost net comes from. This is why (20) ____, which mainly occurs in international waters. Unfortunately, as long as there is no effective international control system, fishing ships can continue to leave their old nets in the sea without punishment.