**Core Concept**
Antiandrogenic drugs are a class of medications that block the action of androgens, such as testosterone, thereby reducing their effects on the body. These drugs are used to treat conditions like prostate cancer, acne, and hirsutism, as well as to suppress androgen secretion in patients with androgen-dependent tumors.

**Why the Correct Answer is Right**
The correct answer is an antiandrogenic drug because it binds to androgen receptors, preventing testosterone from exerting its effects on target tissues. This action is mediated by the drug's ability to competitively inhibit the binding of testosterone to androgen receptors, thereby reducing the expression of androgen-dependent genes.

**Why Each Wrong Option is Incorrect**
**Option A:** This is not an antiandrogenic drug because it is a selective estrogen receptor modulator (SERM), which acts on estrogen receptors rather than androgen receptors.
**Option B:** This is not an antiandrogenic drug because it is an aromatase inhibitor, which reduces estrogen production by inhibiting the enzyme aromatase, but does not directly block androgen action.
**Option C:** This is not an antiandrogenic drug because it is a GnRH agonist, which suppresses gonadotropin secretion and thereby reduces androgen production, but does not directly block androgen action.

**Clinical Pearl / High-Yield Fact**
Antiandrogenic drugs can cause gynecomastia (breast enlargement in males) as a side effect due to the imbalance of estrogen and testosterone levels.

**Correct Answer:** C. Flutamide