**Core Concept**
The **pelvic bones** exhibit various features that can be used to determine the sex of an individual, with an accuracy of up to 99%. These features include the shape and size of the **pelvic inlet**, **outlet**, and **midplane**, as well as the **subpubic angle** and **sciatic notch**.

**Why the Correct Answer is Right**
Since the correct answer is not provided, let's discuss the general approach to determining sex differences in pelvic bones. The **subpubic angle** and **sciatic notch** are key features used to differentiate between male and female pelvises. However, one feature that is not reliable for sex determination is the **vertex of the sacrum**, as it can vary greatly between individuals.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option details, it's challenging to provide a precise explanation. However, features like the **subpubic angle** and **sciatic notch** are generally reliable for sex determination.
**Option B:** Similarly, without the specific option, it's difficult to comment. Nevertheless, the **shape of the pelvic inlet** can be used to determine sex.
**Option C:** Again, lacking the specific option, we can't provide a detailed explanation. Nonetheless, the **ischiopubic index** is another feature that can help determine sex.
**Option D:** Assuming this option might relate to a less reliable feature, it's essential to remember that individual variations can limit the accuracy of sex determination.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that while many features of the pelvic bones can be used to determine sex with high accuracy, individual variations and exceptions can occur. It's crucial to consider multiple factors when assessing the pelvis for sex determination.

**Correct Answer:** D. Vertex of the sacrum