**Core Concept**
The **ceiling effect** refers to a phenomenon where beyond a certain dose, the intensity of the drug's effect no longer increases. This is a key principle in **pharmacodynamics**, which studies the biochemical and physiological effects of drugs and their mechanisms of action.

**Why the Correct Answer is Right**
Since the correct answer is not provided, I will explain the concept in general. Drugs that exhibit a **ceiling effect** typically have a maximal efficacy beyond which further increases in dose do not produce additional effects. This is often seen in **opioid analgesics** and **beta-blockers**.

**Why Each Wrong Option is Incorrect**
**Option A:** Without knowing the specific drugs listed, we cannot directly address why each option is incorrect. However, typically, options that do not exhibit a **ceiling effect** would include drugs where the effect increases with the dose without a clear maximum, such as certain **antibiotics** or **anticancer drugs**.
**Option B:** Similarly, without specifics, we can say that drugs not showing a **ceiling effect** might include those where the dose-response curve continues to rise without an evident plateau.
**Option C:** and **Option D:** would be incorrect for the same reason, lacking the characteristic plateau in their dose-response curves.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the **ceiling effect** is crucial for understanding the limits of a drug's efficacy and safety profile. Recognizing which drugs exhibit this effect can help clinicians avoid unnecessary dose escalations and potential toxicity.

**Correct Answer:** Unfortunately, without the specific options provided, the correct answer cannot be determined.