钩端螺旋体的显微镜凝集试验,单份血清标本有诊断意义的滴度是()
A.1:100
B.1:200
C.1:300
D.1:400
E.1:500
参考答案:C
The radiotelegraph alarm signal is().
A.SOS sent three times
B.ten one-second dashes with a four-second interval between them
C.twelve four-second dashes with a one-second interval between them
D.twelve one-second dashes with a short interval between them
控制农药对食品污染及危害的措施有哪些?