**Core Concept**
Soyabean is a legume that contains high amounts of protein, isoflavones, and other nutrients. It is a rich source of phytoestrogens, which can mimic the effects of estrogen in the body.

**Why the Correct Answer is Right**
The isoflavones present in soyabean, particularly genistein and daidzein, can bind to estrogen receptors in the body, influencing hormone-sensitive tissues. This can lead to various physiological effects, including the reduction of hot flashes and night sweats in postmenopausal women. The bioavailability of isoflavones is enhanced when soyabean is fermented, such as in the production of tempeh or miso.

**Why Each Wrong Option is Incorrect**
**Option A:** Not relevant to the context of soyabean.
**Option B:** Soyabean is not typically associated with significant amounts of vitamin C.
**Option C:** Soyabean is not a primary source of vitamin B12.

**Clinical Pearl / High-Yield Fact**
Soyabean consumption has been associated with improved cardiovascular health, possibly due to its isoflavone content and ability to lower LDL cholesterol levels.

**Correct Answer:** D.