选择合适的成盐形式分离麻黄碱和伪麻黄碱生物碱()
A.盐酸盐
B.酒石酸盐
C.草酸盐
D.硫酸盐
E.碳酸盐
参考答案:C
Since my return to China, I haven’t seen my host mother in America; nor______from her.
A.I heard
B.I have heard
C.did I hear
D.have I heard
下列施工方式中,属于组织施工的基本方式的是()
A.分别施工
B.依次施工
C.流水施工
D.间断施工
E.平行施工