What was the cure for the Black Death during the Middle Ages?

Some of the cures they tried included: Rubbing onions, herbs or a chopped up snake (if available) on the boils or cutting up a pigeon and rubbing it over an infected body. Drinking vinegar, eating crushed minerals, arsenic, mercury or even ten-year-old treacle!

it was mostly cured by quarantine

Explanation:

The uninfected would typically remain in their homes and only leave when it was necessary

yup! you are correct it is b.

the graph shows the spread of railways in the 1800s.

based on the graph, the conclusion that can be drawn about germany is answer d)   by 1880, germany had more rail lines than great britain and russia.