能加速生物活性物质释放,引起哮喘发作有()
A.迷走神经兴奋
B.交感神经兴奋
C.细胞内cGMP浓度增高
D.细胞内cAMP浓度增高
E.细胞内cAMP浓度降
参考答案:A, C, D
.
________ the absence of any further evidence the police were unable to solve the murder.
A.For
B.From
C.On
D.In
污染等级是如何划分的?共分几级?