最易发生变异而造成疾病流行的病原体是()
A.流行性脑膜炎球菌
B.流行性乙型脑炎病毒
C.流行性出血热病毒
D.流行性感冒病毒
E.流行性感冒杆菌
参考答案:D
____ their work, they had a rest. [ ]
A. Having finished
B. Finished
C. Having been finished
D. Finishing
固定消防炮系统主要系统组件的外表面宜涂为红色。()