**Core Concept**
The question is testing the understanding of the **Gravida/Para** system, which is used to describe a woman's pregnancy and childbirth history. This system is essential in **obstetrics** to assess the risk and complexity of pregnancies. The terms **Gravida** and **Para** refer to the number of times a woman has been pregnant and the number of times she has given birth, respectively.

**Why the Correct Answer is Right**
A woman who has had 4 pregnancies, one of which is a twin pregnancy, would be considered a **Gravida 4** because she has been pregnant 4 times. However, when calculating her **Parity**, each pregnancy that resulted in a birth is counted, regardless of whether it was a single or multiple birth. Since one of her pregnancies was a twin pregnancy, she has given birth a total of 5 times (3 single pregnancies + 1 twin pregnancy). Therefore, she would be designated as a **Gravida 4, Para 5**.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately reflect the number of pregnancies or births.
**Option B:** This option is incorrect because it undercounts the number of births.
**Option C:** This option is incorrect because it miscounts both the number of pregnancies and the number of births.

**Clinical Pearl / High-Yield Fact**
It's crucial to remember that when documenting a woman's obstetric history, **Gravida** refers to the number of pregnancies, and **Para** refers to the number of viable births (including multiple births as one event).

**Correct Answer:** D. Gravida 4, Para 5.