Peasant workers began to demand higher wages after the outbreak of the black plague because
a. foreign trade increasedb. less land was availablec. there was a shortage of workersd. working conditions were more hazardous

C. there was a shortage of workers

Explanation:

    Undoubtedly the greatest consequence of the Black Death was its worldwide socio-economic impact, caused by the great death, especially in Europe and Asia. The world's population is estimated to have shrunk from just over 400 million to 300 million, a loss of over 25%. The most affected regions were Florence, which lost 58 percent of its population, Egypt, which lost just over 40 percent, and the German cities of Bremen and Hamburg, which lost more than 60 percent each.

    With the decimation of a third of the European population by the Black Death, landlords saw a considerable decrease in the available labor force, which increased their exploitation of existing labor.

  The servants realized that it was time to claim better living conditions, provoking serious peasant revolts. Meanwhile, the bourgeoisie was also revolting against the oppression exercised by the lords over the cities.

a and b because with the other three, they simplify to something else.