**Core Concept**
Estrogen is a crucial sex hormone that plays a vital role in the development and maintenance of female reproductive and sexual characteristics. It exerts its effects through various mechanisms, including the regulation of gene expression, enzyme activity, and the modulation of cellular responses.

**Why the Correct Answer is Right**
Estrogen actually decreases osteoclast activity and increases osteoblast activity, leading to an overall increase in bone density. This is in contrast to androgens, such as testosterone, which stimulate osteoclast activity and can lead to bone resorption. The correct answer is incorrect because it states that estrogen stimulates osteoclasts, which is a false statement.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is true. Estrogen is essential for the development of secondary sex characteristics in females, such as breast development, widening of the hips, and the growth of pubic and axillary hair.

**Option C:** This statement is true. Estrogen has been shown to have a favorable effect on lipid profiles, including a decrease in low-density lipoprotein (LDL) cholesterol, also known as "bad" cholesterol.

**Option D:** This statement is true. Estrogen has a coagulative effect on the blood, increasing the risk of thrombosis and thromboembolism. This is why estrogen-containing medications, such as birth control pills, carry a warning about the risk of blood clots.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that estrogen has a protective effect on bone density, and its deficiency can lead to osteoporosis and increased risk of fractures. This is why hormone replacement therapy (HRT) is often recommended for postmenopausal women to alleviate symptoms of estrogen deficiency.

**✓ Correct Answer: B. Stimulates osteoclasts. This statement is false, as estrogen actually decreases osteoclast activity.**