Step 1: Recognize hallmark symptom.
Auditory hallucinations—hearing voices or sounds without external stimuli—are the {most common} hallucinations in schizophrenia, often commenting or conversing.
Step 2: Rule out other options.
Simple phobias/anxiety typically show autonomic arousal and catastrophic thoughts, {not} true hallucinations. “Mental deficiency” (intellectual disability) is a neurodevelopmental condition, not characterized by psychotic hallucinations.
Step 3: Conclude.
\[
\boxed{\text{Schizophrenia (Option A).}}
\]