Tom was very glad          to attend the ceremony. [ ]

A. being allowed      

B. to have been allowed

C. having allowed  

D. to have allowed

某学校119名学生在同一餐中因食入同一种食物而相继出现腹痛、腹泻、发热等症状，被诊断为一起食源性疾病，其判断是“食源性肠道传染病”还是“食物中毒”的依据是

A．是否均由相同食物引起
B．症状是否基本一致
C．是否有人传人现象(是否有流行病学余波)
D．实验室中是否检出原因微生物
E．是否有死亡