Task: Question Answering
Input (English): Problem: a dog is tied to a tree by a long nylon cord . if the dog runs from the due north side of the tree to the due south side of the tree with the cord extended to its full length at all items , and the dog ran approximately 30 feet , what was the approximate length of the nylon cord l in feet ? 
Options: a ) 30 , b ) 25 , c ) 15 , d ) 10 , e ) 5
Output (English): d