2.5×0.4÷2.5×0.4
=1÷1
=1
Your idea about having a picnic tonight .
辨别下面所叙述的几种事实
①一个乳酸菌
②培养皿中的乳酸菌菌落
③培养基被污染后,除乳酸菌外,又滋生了真菌以及大肠杆菌等其他细菌.
回答下列问题:它们各属于生命系统的哪项结构层次?
①____ ;②____;③____.
—Have you ever been to America?
—No, I have been there.