**Core Concept**
Skinner's operant conditioning theory explains how behavior is modified by its consequences. There are four main types of conditioning: positive reinforcement, negative reinforcement, punishment, and omission (or extinction). Omission occurs when a behavior is followed by the absence of a previously presented stimulus, leading to a decrease in the behavior.

**Why the Correct Answer is Right**
In this scenario, the dentist removes the mother from the operatory (a previously presented stimulus) after the child's tantrum. This absence of the stimulus (the mother's presence) leads to an increase in the desired behavior (cooperation). The child learns that the absence of the mother is associated with better behavior, resulting in a decrease in tantrums. This type of conditioning is known as omission or extinction.

**Why Each Wrong Option is Incorrect**
**Option A:** Positive reinforcement occurs when a behavior is followed by the presentation of a stimulus, such as a reward. In this case, the dentist removes the mother, not presents a reward.

**Option B:** Negative reinforcement occurs when a behavior is followed by the removal of an aversive stimulus. While the mother's presence may be aversive to the child, the dentist's action is not removing an aversive stimulus, but rather removing a stimulus that was present.

**Option D:** Punishment occurs when a behavior is followed by an aversive stimulus. In this case, the dentist's action is not presenting an aversive stimulus to the child, but rather removing a stimulus.

**Clinical Pearl / High-Yield Fact**
Skinner's operant conditioning theory has significant implications for behavior modification in various settings, including dentistry. Understanding the principles of operant conditioning can help dentists and healthcare providers design effective behavioral interventions and avoid common pitfalls.

**✓ Correct Answer: C. Omission. The example demonstrated by the dentist falls under omission, a type of operant conditioning where a behavior is followed by the absence of a previously presented stimulus.**