**Core Concept**
Drug resistance in bacteria refers to the acquired ability of microorganisms to resist the effects of antibiotics. This resistance can be intrinsic, meaning it is present from birth, or it can be acquired through genetic mutations or horizontal gene transfer.

**Why the Correct Answer is Right**
Drug resistance is not transmitted through physical contact or direct transfer of resistant bacteria. However, it can be spread through the horizontal transfer of resistance genes between bacteria, often facilitated by plasmids. This process allows resistant bacteria to share their resistance genes with other susceptible bacteria, contributing to the development of widespread antibiotic resistance. The primary mechanism of horizontal gene transfer is conjugation, where a plasmid is transferred from a donor bacterium to a recipient bacterium through a specialized structure called a conjugation pilus.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because drug resistance can be transmitted vertically through genetic mutations that occur during the replication of bacterial DNA. These mutations can result in changes to the target of an antibiotic, making the bacteria resistant to its effects.

**Option B:** This option is incorrect because drug resistance can be transmitted horizontally through the transfer of resistance genes between bacteria. This can occur through conjugation, transformation, or transduction.

**Option C:** This option is incorrect because drug resistance can be transmitted through the use of antibiotics, which can select for resistant bacteria that are more likely to survive and multiply. This process is known as selective pressure.

**Clinical Pearl / High-Yield Fact**
It is essential to note that antibiotic resistance is a significant public health concern, and the overuse or misuse of antibiotics can contribute to the development of resistance. To mitigate this issue, it is crucial to use antibiotics judiciously and to follow established guidelines for their use.

**Correct Answer:** D.