The erroneous practices used during the bubonic plague outbreak in europe to slow the spread of the disease included 1.penicillin injections 2.putting patients in solitary confinement (quarantine) to keep other's from getting sick 3.quarantine the household all together. 4.allow the sick to lay out in sunshine to purify the skin and lungs.

The correct answer should be 3.Quarantine the household all together.

They couldn't quarantine only one person because they didn't know whether their family also got it and they also believed that the diseases could be transferred from the possessions of the people who had it. This is why they would quarantine an entire house and if they died they would often burn the entire house down.

Your answer would be a in this question good luck