**Core Concept**
Anencephaly is a severe congenital anomaly characterized by the absence of a major portion of the brain, skull, and scalp. It is a form of neural tube defect (NTD) that occurs during embryonic development. The diagnosis of anencephaly relies on the visualization of characteristic ultrasound (USG) findings.

**Why the Correct Answer is Right**
Anencephaly can be diagnosed by USG as early as 10-14 weeks of gestation with high accuracy. The diagnosis is based on the absence of the cranial vault and the presence of a small, underdeveloped brain. The open neural plate and the absence of the forebrain and midbrain structures are also characteristic features. The USG findings in anencephaly are distinct, and the diagnosis can be confirmed by the absence of the normal fetal skull and scalp.

**Why Each Wrong Option is Incorrect**
* **Option A:** 16-20 weeks of gestation - While anencephaly can be diagnosed later in pregnancy, it is not the earliest possible time point for diagnosis.
* **Option B:** 24-28 weeks of gestation - This time frame is too late for the diagnosis of anencephaly, which can be detected earlier in pregnancy.
* **Option C:** 30-34 weeks of gestation - This is even later than Option B and is not a suitable time frame for the diagnosis of anencephaly.

**Clinical Pearl / High-Yield Fact**
Anencephaly is one of the most common types of neural tube defects, and it is often associated with other congenital anomalies, such as heart defects and limb abnormalities.

**Correct Answer:** C. 10-14 weeks of gestation.