**Core Concept**
The question is testing the student's knowledge of **muscle pathology**, specifically the characteristic features of **skeletal muscle** under microscopic examination. Linear striations are a hallmark of skeletal muscle, resulting from the regular arrangement of **sarcomeres**.

**Why the Correct Answer is Right**
Linear striations are due to the organized structure of **actin** and **myosin** filaments within the **sarcomeres**, giving skeletal muscle its distinctive appearance under the microscope. This regular arrangement allows for efficient muscle contraction.

**Why Each Wrong Option is Incorrect**
**Option A:** Not relevant to muscle structure.
**Option B:** Not relevant to muscle structure.
**Option C:** Not relevant to muscle structure.
**Option D:** Not relevant to muscle structure.

**Clinical Pearl / High-Yield Fact**
Remember that **linear striations** are a key feature distinguishing **skeletal muscle** from **smooth muscle**, which lacks these striations due to its less organized contractile unit structure.

**Correct Answer:** D. Skeletal muscle.