**Core Concept**
The question tests the ability to identify congenital malformations detectable via ultrasound in the first trimester, focusing on **prenatal diagnosis** and **fetal anatomy**.

**Why the Correct Answer is Right**
Although the specific correct answer choice is not provided, typically, major congenital malformations such as **anencephaly** or **holoprosencephaly** can be identified in the first trimester through ultrasound due to significant **cranial abnormalities**. The development of high-resolution ultrasound equipment has improved the detection of these anomalies early in pregnancy.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific details of each choice, we can't directly address why each is incorrect, but generally, options that are incorrect might include conditions that are either too subtle or not typically visible until later in pregnancy.
**Option B:** Similarly, this might involve a condition that doesn't have clear first-trimester ultrasound markers.
**Option C:** Could involve a malformation that requires more developed fetal structures to be visible on ultrasound.
**Option D:** Might be a condition that, while significant, does not have distinguishing features visible in the first trimester.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **anencephaly**, a condition where a major portion of the brain, skull, and scalp are absent, can often be diagnosed between 10-14 weeks of gestation, highlighting the importance of early ultrasound screening for **neural tube defects**.

**Correct Answer:** Correct Answer: D. Anencephaly.