The correct option is B Rickettsia prowazekii
Typhus was the strange disease which brought the grand French army at its knees. This disease was caused by a bacterium called Rickettsia prowazekii. Rickettsia is an obligate intracellular parasitic bacterium that cannot survive for long outside living cells. It is transmitted to humans via external parasites such as human lice. Rickettsia grows in the gut of the lice and is excreted in their faeces. They can remain viable and virulent in the dried faeces for many days. The bacterium gains entry into the human body through the wound caused by the lice bite.