Answer:
In terms of classical conditioning, the sight of the stairs would be described as:
A) conditioned stimulus.
Step-by-step explanation:
When it comes to classical conditioning, we can define a conditioned stimulus as a neutral stimulus that has become associated with an unconditioned stimulus and, eventually, begins to trigger a conditioned response. Diana has associated the stairs with the stumble and injury - unconditioned stimulus and unconditioned response, respectively - she had months ago. The sight of the stairs is now a conditioned stimulus, meaning it causes a conditioned response which is, in this case, the anxiety she feels.