**Core Concept**
Agar is a polysaccharide extracted from red algae, used as a gelling agent in microbiological media. Its unique properties make it an essential component in various laboratory applications.

**Why the Correct Answer is Right**
Agar's gel-like structure is primarily due to its ability to form a hydrogen-bonded network with water molecules. This property allows agar to maintain its shape and provide a solid surface for microorganisms to grow. The agar's gel strength is influenced by factors such as temperature, concentration, and the presence of other substances that can interact with its molecular structure.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is likely incorrect as agar's primary function is not as an emulsifier, although it may exhibit some emulsifying properties due to its amphiphilic nature.

**Option B:**
This option is incorrect because agar's primary function is not as a buffer, although it may exhibit some buffering capacity due to its acidic nature.

**Option C:**
This option is incorrect because agar's primary function is not as an antioxidant, although it may exhibit some antioxidant properties due to its phenolic content.

**Clinical Pearl / High-Yield Fact**
Agar's gel strength can be influenced by the presence of other substances, such as salts or sugars, which can either strengthen or weaken its gel-like structure.

**Correct Answer: B. Agar is used as a gelling agent in microbiological media.**