**Core Concept**
The underlying principle being tested is the concept of **ionization** and its effect on drug **absorption** and **distribution**. Ionization refers to the process by which a drug molecule gains or loses electrons, resulting in the formation of **ions**.

**Why the Correct Answer is Right**
A highly ionized drug is more **water-soluble** and less **lipid-soluble**, which affects its ability to cross **cell membranes**. Since cell membranes are **lipid bilayers**, non-ionized (lipid-soluble) drugs can cross more easily than ionized (water-soluble) drugs.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because ionization does not directly increase lipid solubility.
**Option B:** Incorrect because high ionization decreases, rather than increases, the ability to cross lipid membranes.
**Option C:** Incorrect because it is the non-ionized form that is more lipid-soluble.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the **pH** of the environment can significantly affect the ionization state of a drug, thereby influencing its absorption and distribution.

**Correct Answer:** D. Poor absorption from the gut due to high water solubility.