Due to fierce survival competition in its ecological area, the number of elderly elephants is decreasing year by year, and the survival rate of young elephants has also greatly increased. Continue this way, it is foreseeable within two years. ['The number of older elephants will be less than the number of young elephants.', 'Proportion of juvenile elephants will increase.', 'The proportion of young elephants will decrease.', 'The proportion of young elephants will increase.']