**Core Concept**
Breslau's second life test is a forensic examination used to determine if a newborn infant was stillborn or if it was born alive and then murdered. This test involves examining the organs for changes that occur when an infant takes its first breath after birth, which can indicate that the infant was indeed born alive.

**Why the Correct Answer is Right**
The correct answer is the stomach and intestine because these organs undergo significant changes when an infant takes its first breath, including the release of gastric and intestinal enzymes. This is due to the presence of oxygen in the air, which triggers the release of these enzymes. The test involves examining the stomach and intestine for signs of these enzymatic changes, such as the presence of bile in the duodenum or the presence of oxygen in the intestinal contents. This is a crucial indicator of whether the infant was born alive or not.

**Why Each Wrong Option is Incorrect**
**Option A:** The brain is not the primary organ examined in Breslau's second life test, although changes in the brain can occur after birth. However, these changes are not as reliable or specific as the changes observed in the stomach and intestine.
**Option B:** The heart is not directly involved in Breslau's second life test, as the primary focus is on the changes that occur in the digestive system after birth.
**Option C:** The lung is examined in Breslau's first life test, not the second. The first test involves examining the lungs for signs of expansion and aeration, which can indicate that the infant took its first breath.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Breslau's second life test is a specific examination technique used to determine if an infant was born alive, and it relies on the changes that occur in the stomach and intestine after the first breath. This test is crucial in forensic medicine, particularly in cases of suspected infanticide.

**✓ Correct Answer: D. Stomach and intestine**