From the symptoms shown in the dead body, he ________to death by a certain poisonous chemical,

but I can't tell exactly which. [ ]

A. must have been poisoned    

B. should have been poisoned

C. could have been poisoned      

D. may have been poisoned

下列关于Ⅱ型变态反应的描述正确的有()

A．常见Ⅱ型变态性疾病有输血反应、新生儿溶血疾病

B．又称细胞溶解型变态反应，主要抗体为lgG和IgM

C．由机体组织细胞上的抗原与相应抗体发生免疫反应

D．发生机制有三方面，即激活补体导致细胞溶解，吞噬细胞作用及抗体依赖的细胞介导的细胞毒性作用

E．组胺释放在早期阶段起重要作用