题目内容

Did you do what l _________ you to do yesterday?

A. have told
B. had told
C. had been telling
D. tells

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We were hurrying because we thought the bell _________ .

A. had already rang
B. has already rang
C. had already rung
D. rang

从混杂细菌标本中分离病原菌用( )

A. 革兰氏染色镜检
B. 平板划线培养法
C. 半固体穿刺接种
D. 用暗视野显微镜观察
E. 纯培养法

细菌的外毒素大多在下列哪期产生( )

A. 稳定期
B. 对数生长期
C. 衰退期
D. 迟缓期
E. 以上都不对

细菌生长繁殖的营养物质包括( )

A. 水
B. 碳源
C. 氮源
D. 无机盐
E. 生长因子