**Core Concept**
Electron microscopy is a type of microscopy that uses a beam of electrons to produce an image of the specimen. This technique is particularly useful for visualizing the ultrastructure of cells and tissues at high resolution.

**Why the Correct Answer is Right**
Electron microscopy is not typically used for observing the motility of microorganisms. This is because the technique requires the specimen to be fixed and stained, which would prevent the microorganisms from moving. Additionally, electron microscopy is often used to study the morphology and ultrastructure of cells and tissues, rather than their functional properties such as motility.

**Why Each Wrong Option is Incorrect**
**Option A:** Electron microscopy is commonly used for studying the ultrastructure of cells and tissues, including the morphology of microorganisms such as bacteria and viruses. This makes option A a plausible distractor.
**Option B:** Electron microscopy can be used to study the morphology of cells, including their surface features and ultrastructure. This makes option B a plausible distractor.
**Option C:** Electron microscopy can be used to study the ultrastructure of tissues, including the morphology of cells and their interactions. This makes option C a plausible distractor.

**Clinical Pearl / High-Yield Fact**
Electron microscopy is a powerful tool for studying the ultrastructure of cells and tissues, but it requires the specimen to be fixed and stained, which can compromise the functional properties of the specimen.

**Correct Answer:** A. Electron microscopy is used for observing the ultrastructure of cells and tissues, not for studying the motility of microorganisms.