The toxin produced by tetanus germs affects:

In which organ do the bacteria of pneumonia cause the accumulation of fluid?

$Yersinia pestis$ is responsible for:

Koch's postulates are not applicable to which of the following?

Typhoid fever is most common in which age group?

Which bacteria are responsible for pneumonia?
$(i)$ $Streptococcus$ $typhi$
$(ii)$ $Haemophilus$ $influenzae$
$(iii)$ $Streptococcus$ $pneumoniae$
$(iv)$ $Haemophilus$ $typhi$