**Core Concept**
The transmission of R factors refers to the transfer of plasmids that carry antibiotic resistance genes between bacteria, leading to the spread of antibiotic resistance. R factors are small, self-replicating DNA molecules that can be transferred between bacteria through conjugation, transformation, or transduction.

**Why the Correct Answer is Right**
R factors are typically transferred through conjugation, a process in which a donor bacterium directly transfers the plasmid to a recipient bacterium through a specialized structure called a conjugation pilus. This process allows for the efficient transfer of R factors between bacteria, contributing to the development of antibiotic resistance. The conjugation process involves the interaction of the donor and recipient bacteria, as well as the presence of a sex pilus, which facilitates the transfer of the plasmid.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while transformation and transduction are mechanisms of gene transfer, they are not the primary means of R factor transmission.
**Option B:** This option is incorrect because while plasmids can be transferred through conjugation, transformation, or transduction, the specific mechanism of R factor transmission is conjugation.
**Option C:** This option is incorrect because while R factors can be transferred through conjugation, the presence of a sex pilus is a necessary component of the conjugation process, making this option incomplete.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the transmission of R factors through conjugation contributes to the spread of antibiotic resistance among bacteria, making it a critical concern in the development of antibiotic resistance.

**Correct Answer: C. Conjugation. This is the primary mechanism of R factor transmission.**