**Core Concept**
The intrinsic muscles of the tongue play a crucial role in changing its shape, which is essential for functions like speech and swallowing. These muscles include the **longitudinal**, **transverse**, and **vertical** muscles. The **longitudinal muscles** are further divided into **superior** and **inferior** parts.

**Why the Correct Answer is Right**
The correct answer is related to the function of shortening the tongue, which involves the **inferior longitudinal muscle**. This muscle runs from the root of the tongue to the apex, and when it contracts, it shortens the tongue. The mechanism involves the contraction of the **inferior longitudinal muscle**, which pulls the tongue anteriorly, thereby shortening it.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not correspond to the muscle responsible for shortening the tongue.
**Option B:** Similarly, this option does not match the function of shortening the tongue.
**Option C:** This option is also incorrect as it does not relate to the shortening function.
**Option D:** This is not the correct answer as it is not associated with the shortening of the tongue.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the **intrinsic muscles** of the tongue are responsible for its shape and movements, and each has a specific function, such as shortening, lengthening, or changing the tongue's width.

**Correct Answer:** D. Inferior longitudinal muscle