What<br/>is the preparation of Bacillus Calmette-Guerin based on?() A: virulence<br/>variation B: structure<br/>variation C: morphology<br/>variation D: colony<br/>variation E: drug<br/>resistance variation

Which statement about apparent infection is not right? A: Significant signs and symptoms are found clinically; B: The pathogens would be eliminated completely after recovery from infection; C: Pathogens could be transmitted to other persons; D: The bacterial virulence is higher, the host immunity is weaker;

Ti质粒上除了介导DNA转移的T-DNA片段外,还有() A: 致毒Vir(virulence<br/>region)基因 B: 植物生长素和分裂素合成基因 C: 乙酰丁香酮合成基因 D: 冠瘿碱合成基因

Which<br/>one of the following is the reason of pandemic<br/>flu<br/>() A: virus<br/>has strong virulence <br/>(B)HA<br/>of Influenza B: virus<br/>easily produce variation, and people lack of immunity <br/>(C)<br/>NA of Influenza C: virus<br/>easily produces variation, and people lack of immunity<br/>(D)<br/>Influenza D: virus<br/>develops new subtype virus, and people lack of immunity