Task: Question Answering
Input (English): Problem: a certain bacteria colony doubles in size every day for 19 days , at which point it reaches the limit of its habitat and can no longer grow . if two bacteria colonies start growing simultaneously , how many days will it take them to reach the habitat ’ s limit ? 
Options: a ) 6.33 , b ) 7.5 , c ) 10 , d ) 18 , e ) 19
Output (English): d