观察右边一组单项式：x，-3x2，9x3，-27x4，…
生物多样性不包括（ ）
关于电与磁的有关知识，下列说法中正确的是（ ）
— Would you mind my using your car?— . Here is the key.
This question is so hard that very ______ students can answer it.
