Final answer:
A resistant bacterium can share its resistance with its neighbors primarily through conjugation, but also via processes like transformation and transduction.
Step-by-step explanation:
A resistant bacterium can share its resistance with its neighbors through several processes, but the correct choice from the listed options is conjugation. During conjugation, DNA is transferred from one cell to another via a mating bridge, which is an extension that forms between two bacterial cells. Additionally, transformation is another process where bacteria can pick up antibiotic resistance genes from their environment, and transduction is a method where bacterial DNA is transferred from one bacterium to another by a virus (bacteriophage).