Respuesta :
ANSWER:
The correct option is "The number of mice decreased".
EXPLANATION:
It is clearly given in the question that the snakes depended on the mice for their survival. The snakes fed on the mice on the field. When the new method of grain spill was found, the mice could not find enough grain to eat and therefore they either left the field or died because of hunger.
`The reduced population of mice was not enough for the snakes which in turn either died or moved to another place for survival.