Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: Given the rise in global temperatures, it would be fair to assume glaciers around the world are all melting and retreating, but a series of new GIFs suggests otherwise. Time-lapse animations show 'rivers of ice' in northern Pakistan, expanding, contracting and surging forwards. A Swiss researcher compiled the clips of glaciers in the Karakoram range using 25 years of Landsat satellite images, and they show many glaciers in the region are actually increasing in size. Dr Frank Paul at the University of Zurich in Switzerland created four GIFS, which are made from combined and compressed satellite images. Each GIF shows 25 years of glacier movement in just one second taken from four regions - Baltoro, Panmah, Skamri–Sarpo Laggo, and Shaksgam – in the central Karakoram.Animations show glacier movements accelerated by 800 million timesSatellite images taken over 25 years were combined to create time-lapsesMany glaciers in the Karakoram range are actually increasing in sizeCurious 'surge' behaviour makes them move 100 times faster than usual 
 Question:He then used free software to create a looping animation for each of the four _ regions.

Karakoram