A:碳酸氢铵
B:硝酸钾
C:尿素
D:过磷酸钙
I was greatly ________ at how he worked out the ________ problem in a creative way.
如图,抛物线y=a(x﹣h)2+k经过点A(0,1),且顶点坐标为B(1,2),它的对称轴与x轴交于点C.
读拼音,写句子。
wǒ men shì zǔ guó de huā duǒ
____