In which age group is typhoid most common?

Which of the following conditions can be cured by $Doxycycline$ treatment?

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

Diphtheria is caused by

Salmonella typhosa causes

Given below are two statements $:$
Statement-$I$ : Typhoid fever can be confirmed by the Widal test.
Statement-$II$ : Intestinal perforation and death may occur in severe cases of typhoid.
In the light of the above statements,choose the correct answer from the options given below $:$