How do these humors get out of balance? This is where the overlapping ideas of Elizabethan medicine might leave you a little confused. By far the most important cause is divine intervention. People believe that illnesses may be sent to punish them for a sin—or simply because God wants them to die and go to Heaven. Some hold that God, by sending them an illness, is giving them a chance to atone for some previous transgression through suf­fering, and so they are thankful for their affliction. –The Time Traveler's Guide to Elizabethan England,
Ian Mortimer

How does the passage develop the central idea "Elizabethans believed that health depended on the balance of the four humors"?

It explains that Elizabethans could control the balance of their humors.
It explains that Elizabethans blamed what they ingested for the imbalance of humors.
It explains that Elizabethans believed that age was responsible for imbalanced humors.
It explains that Elizabethans believed that divine intervention caused imbalanced humors.