下列生态系统中被誉为“地球之肾”之称的是( )
A:海洋生态系统
B:淡水生态系
C:森林生态系统
D:湿地生态系统
按要求,写单词。
sheep(复数)____
—I hope that what we have said will not fall on deaf ears.
— Don’t worry. It’s good for their study. They will follow it.
函数y=sin(2x-π3)与y=cos(2x+2π3)的图象关于直线x=a对称,则a可能是( )