The correct answer is C. Vacilate. The correct spelling is "vacillate".
- Vacuum: a space entirely empty of matter.
- Vaccinate: to protect someone from a disease by giving them an injection of a weakened or killed form of the disease.
- Varnish: a liquid that is applied to wood or other surfaces to give them a hard, shiny finish.
- Vacilate: to move or swing from one side to the other, or to change one's mind frequently.
The word "vacilate" is misspelled because it has an extra "i". The correct spelling is "vacillate".
