The correct answer is eject.
C. engage in combat on horseback
The correct answer is (A) To eject; to expel (from a position or place); to get rid of; to deprive of; to drive out; to force out; to put out of possession; to take away (a right, privilege, etc.); to dispossess of.
Oust comes from Old French oster (to remove), Latin obstare (to stand in the way, oppose).
Examples of use:
- As soon as he had purchased the building, he ousted the tenants.
- The shareholders ousted the previous board of directors and CEO.