**Core Concept**
The patient's presentation of a red dot on fundoscopic examination, combined with a history of trauma, suggests a retinal hemorrhage. This is a type of bleeding in the retina, which is the light-sensitive tissue at the back of the eye. The retina is responsible for converting light into electrical signals that are transmitted to the brain.

**Why the Correct Answer is Right**
The patient's history of being hit by a tennis ball likely caused a blunt ocular trauma, which led to a retinal hemorrhage. The force of the impact may have caused blood vessels in the retina to rupture, resulting in bleeding. The red dot seen on fundoscopic examination is likely a representation of this hemorrhage on the retina's surface. The retina's delicate blood vessels are prone to damage from trauma, making it a common site for hemorrhages in cases of blunt ocular trauma.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while a retinal tear can cause a retinal detachment, it does not explain the presence of a red dot on fundoscopic examination.

**Option B:** This option is incorrect because a diabetic retinopathy is a chronic condition that affects the blood vessels in the retina, but it is not directly related to a history of trauma.

**Option C:** This option is incorrect because a retinal detachment is a more serious condition where the retina separates from the underlying tissue, but it does not explain the presence of a red dot on fundoscopic examination.

**Option D:** This option is incorrect because a choroidal melanoma is a type of cancer that affects the choroid layer of the eye, but it is not directly related to a history of trauma.

**Clinical Pearl / High-Yield Fact**
In cases of blunt ocular trauma, it is essential to perform a thorough eye examination, including fundoscopy, to rule out retinal hemorrhages and other ocular injuries. A prompt diagnosis and treatment can help prevent long-term vision loss.

**Correct Answer:** C.