A：豹种群基因多样性增加
B：豹后代的性别比例明显改变
C：物种丰富度出现大幅度下降
D：豹种群的致病基因频率不变
In April, the weather in some places in Shanxi was really changeable. People still remember they have _______ four seasons in a week.
拥有愉快的心情是中学生心理健康的核心．下列不利于调适情绪的是（ ）
下列有关生态系统的叙述正确的是（ ）
