Definition: In this task, you need to provide the correct option for a given problem from the provided options.
Input: Problem: the ratio of 2 numbers is 1 : 2 and their h . c . f . is 10 . their l . c . m . is ? 
Options: a ) 10 , b ) 20 , c ) 30 , d ) 50 , e ) 40
Output:
b