**Core Concept**
The ductus venosus is a vital shunt in the fetal circulation that connects the umbilical vein to the inferior vena cava, allowing oxygenated blood from the placenta to bypass the liver and directly reach the heart. After birth, this shunt closes, and the ductus venosus obliterates.

**Why the Correct Answer is Right**
The remnant of the ductus venosus is the ligamentum venosum, which is a fibrous remnant of the ductus venosus that remains after birth. This ligament is located on the undersurface of the left lobe of the liver and serves as a landmark for surgical procedures. The ligamentum venosum is a remnant of the ductus venosus because it is formed from the obliterated ductus venosus, which closes shortly after birth.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the ligamentum teres, also known as the round ligament of the liver, is the remnant of the umbilical vein, not the ductus venosus.
**Option B:** This option is incorrect because the ligamentum arteriosum is the remnant of the ductus arteriosus, not the ductus venosus.
**Option C:** This option is incorrect because the falciform ligament is a fibrous structure that attaches the liver to the anterior abdominal wall, but it is not a remnant of the ductus venosus.

**Clinical Pearl / High-Yield Fact**
The ligamentum venosum is an important landmark for surgeons during hepatic resections and liver transplantations, as it helps to identify the location of the left hepatic vein.

**Correct Answer: C. Ligamentum venosum.**