Which of the Following Is the Best Example of Spreading

Which of the following is the best example of spreading activation at work?

A) Your sensory registers allow you to perceive smooth motion when you move your head.
B) You find it difficult to remember happy things when you are in a bad mood.
C) You find it easy to relearn vocabulary words that you had once learned but forgot.
D) You start thinking about cars, and that leads you to think about trucks and sport-utility vehicles.