Final answer:
The primary emotion being described is fear, as indicated by the use of the word 'afraid' in the sentence about Billy.
Step-by-step explanation:
Billy was afraid to reach into the cavernous dark space under his bed. The primary emotion being described in this sentence is fear. This is evident from the use of the word afraid, which directly indicates that Billy is experiencing fear about the action of reaching under his bed. The sentence conveys a clear psychological state of apprehension and anxiety, thus making Option B the correct answer.
The primary emotion being described in the sentence is fear. Fear is an intense, unpleasant emotion caused by the belief that something dangerous or harmful is happening or will happen. In the sentence, Billy's fear is evident from his reluctance to reach into the dark space under his bed.
This fear is likely due to the unknown and the potential threat that may be lurking beneath the bed. Fear can cause physical and psychological reactions, such as increased heart rate, sweating, and the instinct to avoid or escape from the perceived threat.
Therefore answer is B. Fear.