控制哮喘症状的首选药物是（）
A.β2受体激动剂
B.茶碱类药物
C.抗胆碱药物
D.糖皮质激素
E.色甘酸钠
参考答案：A
The integration of independent states could best be brought about by first creating a central organization with authorities over technical economic tasks.
食品冻结速度越快，则冻结食品的质量越好。（）
