Write a multi-choice question for the following article, with the given choices and answer: Article: Scientists warn today that the Atlantic bluefin tuna faces disappearance unless certain action is taken. They used electronic ways to track the movement of the powerful fish from the Gulf of Mexico to the Mediterranean, and report today in the journal Nature that meals of sushi and sandwiches with tuna worldwide are more dangerous than anyone has imagined. The bluefin tuna can live for 30 years, grow to three metres in length and weigh as much as 700kg. A good one can fetch as much as PS 52,000 in the Tokyo fish markets. "In my lifetime, we've brought this big fish to the doorstep of death in the western Atlantic Ocean," said Barbara Block of Stanford University in California. "The electronic way of tracks provides the best scientific information we've ever had to manage these tuna and we must, as an international community, start to act actively to make sure of the future of this fish. " Scientists have repeatedly said that the harvest of the seas cannot be as good as before. There are fewer and fewer fish in around Newfoundland, North Sea and Iceland, so fishermen have pushed further offshore in search of deep ocean fish. Tuna--in the Mediterranean and Japan--have been under increasing pressure for years. The International Commission on the Conservation of Atlantic Tuna has tried to manage the fish since 1969.There are two populations: a western one that has dropped by 80% in the past 30 years, and a larger, eastern population. Although catches are controlled by 3,000 tons a year in the western fishery, and 32,000 in the east, no one knew whether the limits worked. So Professor Block and her team placed tracks on hundreds of the fish and tracked them to depths of more than 900 metres and on journeys of thousands of miles, measuring the movement, body and water temperatures. "There are two ways to save the Atlantic bluefin tuna--protect them in their production grounds and in their feeding grounds," Prof. Block said. "This will need immediate action in both the central Atlantic, to reduce the loss of the big... Options: A tell people a new way has been found to save the bluefin tuna B call for action to save the bluefin tuna C warn people not to eat tuna sandwiches anymore D help scientists to find a new way to save the bluefin tuna Answer: B call for action to save the bluefin tuna Question:
The purpose of the passage is to _ .