Task: Question Answering
Input (English): Problem: if the sides of a cube are in the ratio 9 : 7 . what is the ratio of their diagonals ? 
Options: a ) 4 : 3 , b ) 16 : 9 , c ) 9 : 7 , d ) 3 : 4 , e ) 3 : 8
Output (English): c