Task: Question Answering
Input (English): Problem: the population of locusts in a certain swarm doubles every two hours . if 4 hours ago there were 1,000 locusts in the swarm , in approximately how many hours will the swarm population exceed 32,000 locusts ? 
Options: a ) 2 , b ) 4 , c ) 6 , d ) 8 , e ) 9
Output (English): c