A:生态系统、个体
B:细胞、生物圈
C:个体、病毒
D:分子和原子、生物圈
一种药品原价每盒25元,经过两次降价后每盒16元.设两次降价的百分率都为x,则x满足( )
We at the party last weekend.
Jenny in a school. Her parents in a hospital.