对于气虚欲脱证最佳的治疗药物是（）
A.党参
B.太子参
C.西洋参
D.人参
E.黄芪
参考答案：D
It was for that reason, I suppose, ____ the book took a long time to come out.[ ]
A. why
B. so
C. that
D. because
简述蓝藻门的主要特征。
