The graph shows, in a period of time between 1978 and 2010. Therefore, it's related to the last 50 years, not the last 100 years, meaning that alternative D is wrong. The amount of sea ice shown in the graph is shown in the scale of million square miles. So, as the graph shows an initial value around 3.2 (3 millions and 2 hundred miles) and it ends up in a value around 2.2 (2 millions and 2 hundred miles), still the real values are around 2.8 (2 million and 8 hundred thousands initially) and 2.0 (2 millions at the end), having a lower value of 1.8 (1 million and 8 hundred thousand); So, in both scenarios, arctic sea ice has shrunk by 1,000,000 (1.0) square miles, being under 2,000,000, not over. Therefore, the highest number to be inside this amount is 2,000, so the correct answer is A: Arctic sea ice has shrunk by over 2,000 square miles in the last 50 years.
