Which of the Following Was Not True of the Janissaries

Which of the following was not true of the Janissaries?

A) Janissaries could not be members of the Sublime Porte.
B) Some of the greatest Ottoman leaders had once been Janissaries.
C) The Janissaries had many opportunities to move up through the ranks of the army.
D) They were Balkan Christian boys who were kidnapped and converted to Islam.
E) They termed themselves "willing slaves of the sultan."