**Core Concept**
Plocquet's test is a method used in forensic medicine to estimate the time since death, specifically in cases of drowning. The test involves calculating the ratio of lung weight to body weight, which is believed to decrease over time due to putrefaction and gas production in the lungs.

**Why the Correct Answer is Right**
Plocquet's test is based on the principle that the lungs are heavier in people who have drowned due to the accumulation of water and gases, such as oxygen, nitrogen, and carbon dioxide. The ratio of lung weight to body weight is calculated to determine the time elapsed since death. This is because the lungs undergo changes in weight and texture over time, which can be used to estimate the post-mortem interval. The calculation of this ratio is a crucial step in Plocquet's test.

**Why Each Wrong Option is Incorrect**
**Option A:** Fodere's test is another method used in forensic medicine to estimate the time since death, but it involves calculating the ratio of the weight of the liver to the weight of the body, not the lungs.
**Option C:** Breslau's second life test is not a well-known or widely used method in forensic medicine, and it does not involve calculating the ratio of lung weight to body weight.
**Option D:** While all three tests are used in forensic medicine, Plocquet's test is the only one that specifically involves calculating the ratio of lung weight to body weight.

**Clinical Pearl / High-Yield Fact**
It's essential to note that Plocquet's test is not a foolproof method for estimating the time since death, as the results can be influenced by various factors, such as the presence of disease or the manner of death. Therefore, it should be used in conjunction with other methods to obtain a more accurate estimate of the post-mortem interval.

**✓ Correct Answer: B. Plocquet's test**