-- What impressed you most during your s

大气中的N₂经固氮后形成的化合物中，哪一组化合物被植物体吸收后可直接用于蛋白质的合成[ ]

A．NH₃和NO₃^-

B．NH₄⁺和NO₂^-

C．NH₄⁺和NH₃

D．NO₃^-和NO₂^-

城市聚落与乡村聚落相比，其最主要差异是

A．房屋建筑的差异

B．人们收入的差异

C．人口数量的差异

D．劳动生产方式的差异

女性，9岁，发烧39℃，咳嗽5天，伴腹痛2天，腹胀，有广泛压痛、反跳痛及肌紧张，肠音弱，腹穿抽出稀薄无臭味脓汁，应首先考虑

A．肠伤寒穿孔

B．肺脓肿破裂

C．阑尾穿孔

D．美克尔憩室穿孔

E．原发性腹膜炎

— She didn't come to school yesterday, did she?

— ______. Though she was not feeling very well. [ ]

A. Yes, she didn't

B. Yes, she did

C. No, she did

D. No, she didn't

带电灭火必须使用不导电的灭火剂，如：干粉灭火器。