**Core Concept**
Relaxin is a hormone that plays a crucial role in pregnancy, particularly in relaxing the pelvic girdle and public symphysis to facilitate childbirth. It also has effects on the cardiovascular system and bone metabolism.

**Why the Correct Answer is Right**
Relaxin is primarily produced by the corpus luteum in the ovaries during early pregnancy. The hormone is released in response to human chorionic gonadotropin (hCG) produced by the placenta. Relaxin acts on the extracellular matrix of connective tissue, breaking down collagen and elastin, which leads to relaxation of the pelvic girdle and public symphysis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the placenta is the primary source of human chorionic gonadotropin (hCG), but it is not the source of relaxin.

**Option B:** This option is incorrect because the pancreas produces insulin and glucagon, but not relaxin.

**Option C:** This option is incorrect because the adrenal glands produce aldosterone, cortisol, and adrenaline, but not relaxin.

**Clinical Pearl / High-Yield Fact**
Relaxin has a unique property of inhibiting the production of osteoclasts, which are responsible for bone resorption. This makes it an important hormone in maintaining bone health during pregnancy.

**Correct Answer: C. Ovaries. Relaxin is primarily produced by the corpus luteum in the ovaries during early pregnancy.**