题目

Pat O’Burke was a poor Irishman with a large family, and one morning, waking up very early from cold and hunger, he decided to go shooting in a wood near his cottage. The wood belonged to Lord Northwood, a rich gentleman. Pat had no right to go there, but in it there were swarms of rabbits and flocks of birds that were good to eat, and Pat determined to take the risk. Suddenly he saw the owner, with a group of friends, coming towards him in the wood. There was a look of anger on Lord Northwood's face as he caught sight of the gun in Pat's hands. Pat's heart sank with fear, but he saw在种群的下列特征中，能预测种群数量变化趋势的是 [     ]A．种群密度B．年龄组成C．性别比例D．出生率和死亡率