下面直接反映了地球大气污染严重的是()
— Yes. She also gives me some ______ on how to learn English well.
已知F1、F2为双曲线C:x24-y2=1的左、右焦点,点P在曲线C上,∠F1PF2=60∘,则P到x轴的距离为( )
下列生物中属于生产者的是( )