**Core Concept**
The posterior tooth that gives better support is determined by its root anatomy, specifically the number and shape of its roots, as well as the presence of any additional supporting structures like the periodontal ligament or surrounding bone.

**Why the Correct Answer is Right**
The tooth that gives better support is typically one with a more extensive root surface area, which is achieved by having multiple roots. This is because the root surface area is inversely proportional to the force exerted on the tooth, allowing for more even distribution of forces. In the case of posterior teeth, the first molar has two large roots (mesial and distal) that provide excellent support, making it a better option compared to other posterior teeth.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it does not specify a posterior tooth, making it an ambiguous choice.
* **Option B:** This option is incorrect as it does not provide any information about the root anatomy of the tooth, which is crucial in determining its support.
* **Option C:** This option is incorrect as it does not specify a posterior tooth with a known root anatomy that provides better support.

**Clinical Pearl / High-Yield Fact**
A good rule of thumb when evaluating the support of a posterior tooth is to look for teeth with a minimum of two roots, as these provide the best support and are less likely to lead to periodontal problems.

**Correct Answer: C. First Molar.**