Which answer matches this clue: the elite imperial guard that protected the emperor and sometimes assassinated him to choose a successor?

• A Urban Cohorts
• B Legio X Fretensis
• C Varangian Guard
• D Praetorian Guard ✓

The Praetorian Guard was established by Augustus; its power grew so great that it auctioned the imperial throne to the highest bidder in AD 193.