**Core Concept**
Fear is a normal human emotion characterized by an intense, unpleasant feeling of anxiety or apprehension. There are several types of fear, each with distinct characteristics and underlying mechanisms. The difficulty in overcoming fear often depends on the type and underlying cause.

**Why the Correct Answer is Right**
The most difficult type of fear to overcome is **Specific Phobia**. This is because specific phobias are intense, irrational fears of specific objects, situations, or activities that are not necessarily related to any real danger. The fear response is often triggered by a conditioned stimulus, such as a snake or a height, which can lead to a strong physiological response, including rapid heartbeat, sweating, and avoidance behaviors. The brain's amygdala plays a key role in processing and storing these fear memories, making it challenging to overcome the phobia through exposure therapy or other treatments.

**Why Each Wrong Option is Incorrect**
**Option A:** Agoraphobia is a type of anxiety disorder characterized by fear of being in public places or crowds. While it can be difficult to overcome, it is not typically as resistant to treatment as specific phobias.

**Option B:** Social Phobia, also known as social anxiety disorder, is a fear of social situations or being judged by others. While it can be challenging to overcome, it often responds well to cognitive-behavioral therapy and medication.

**Option C:** Post-Traumatic Stress Disorder (PTSD) is a condition that develops after a traumatic event, characterized by flashbacks, nightmares, and avoidance behaviors. While it can be difficult to overcome, it often requires specialized treatment and support.

**Clinical Pearl / High-Yield Fact**
To overcome specific phobias, it's essential to understand that the fear response is not rational and that the brain's amygdala is storing the fear memory. Exposure therapy, a type of cognitive-behavioral therapy, can help individuals gradually become comfortable with the feared object or situation.

**Correct Answer:** C.