**Core Concept**
The question is testing the understanding of the concept of "occlusal balance" and the importance of preserving the occlusal relationship between the upper and lower teeth. Occlusal balance is achieved when the upper and lower teeth come into contact in a harmonious and balanced manner, allowing for proper mastication and preventing uneven wear on the teeth.

**Why the Correct Answer is Right**
When the lower premolars and first molar are removed, the occlusal balance is disrupted, and the remaining teeth may not be able to distribute the forces of mastication evenly. If the second molars are not removed, they may be subjected to excessive stress, leading to potential problems such as tooth wear, cracking, or even fracture. This is because the second molars are not designed to handle the full forces of mastication, and removing them can help to redistribute the forces and prevent these problems.

**Why Each Wrong Option is Incorrect**
* **Option A:** Removing the second molars may not necessarily prevent the problems associated with the removal of the lower premolars and first molar. This option is incorrect because it does not address the underlying issue of occlusal balance.
* **Option B:** Preserving the second molars may not be sufficient to restore occlusal balance, especially if the lower premolars and first molar are removed. This option is incorrect because it oversimplifies the complexity of occlusal balance.
* **Option C:** Removing the second molars may not be necessary if the remaining teeth can distribute the forces of mastication evenly. This option is incorrect because it assumes that the remaining teeth can handle the full forces of mastication without any issues.

**Clinical Pearl / High-Yield Fact**
In cases where teeth are removed, it's essential to evaluate the occlusal relationship between the upper and lower teeth and make adjustments as necessary to prevent problems such as tooth wear, cracking, or fracture. This can often be achieved by removing teeth that are not essential for mastication or by using orthodontic appliances to redistribute the forces of mastication.

**Correct Answer: D.**