That boy is Simon. And the girl next to _____ is Amy. [ ]
A. he
B. his
C. him
D. she
答案:C
磷酸二氢铵是一种含有氮、磷两种营养元素的复合肥,熟石灰常可用来中和土壤的酸性,但是这两种物质不宜混合使用,试写出有关反应的化学方程式______,并说明原因______.
简述促进式协调与纠偏式协调。