**Core Concept**
The limbic system is a complex network of brain structures involved in processing emotions, motivation, memory, and other functions essential for human behavior. This system includes the hippocampus, amygdala, hypothalamus, cingulate gyrus, and fornix, among others.

**Why the Correct Answer is Right**
The limbic system plays a crucial role in regulating emotions through the release of neurotransmitters such as dopamine, serotonin, and acetylcholine. The amygdala, a key component of the limbic system, processes emotional information and triggers the body's "fight or flight" response. In addition, the hippocampus is essential for the formation and consolidation of new memories, particularly those related to emotions and experiences. Furthermore, the limbic system is also involved in higher-order functions such as motivation, reward processing, and decision-making.

**Why Each Wrong Option is Incorrect**
**Option A:** While emotions are a primary function of the limbic system, it is not the only function. Therefore, option A is incomplete.
**Option B:** Memory is a critical function of the limbic system, but it is not the only function. The limbic system's role in emotion, motivation, and higher-order functions is equally important.
**Option C:** Higher-order functions are indeed a part of the limbic system's purview, but this option neglects the system's critical roles in emotion and memory.

**Clinical Pearl / High-Yield Fact**
The limbic system's dysregulation has been implicated in various psychiatric disorders, including anxiety, depression, and post-traumatic stress disorder (PTSD). Understanding the limbic system's functions is essential for developing effective treatments for these conditions.

**✓ Correct Answer: D. All**