Task: Question Answering
Input (English): Problem: if a 1 mm thick paper is folded so that the area is halved at every fold , then what would be the thickness of the pile after 50 folds ? 
Options: ['a ) 100 km', 'b ) 1000 km', 'c ) 1 million km', 'd ) 1 billion km', 'e ) none']
Output (English): d