**Core Concept**
Primary amenorrhea is defined as the failure to commence menstruation by the age of 16, in the presence of normal secondary sexual characteristics. This condition can result from a variety of anatomical, hormonal, or genetic abnormalities. The causes of primary amenorrhea can be broadly categorized into disorders of gonadal dysgenesis, chromosomal abnormalities, anatomical abnormalities, and hypogonadotropic hypogonadism.

**Why the Correct Answer is Right**
Asherman's syndrome, also known as intrauterine adhesions or synechiae, is a condition characterized by the formation of scar tissue within the uterus. This condition typically presents with secondary amenorrhea, which is a cessation of menstruation after a normal menstrual history. The formation of adhesions within the uterus can lead to a reduction in the endometrial cavity, resulting in decreased menstrual bleeding. However, Asherman's syndrome is not a cause of primary amenorrhea, as it typically occurs in individuals who have a prior history of normal menstruation.

**Why Each Wrong Option is Incorrect**
**Option A:** Turner's syndrome is a chromosomal abnormality characterized by the presence of a 45,X karyotype, which leads to ovarian dysgenesis and primary amenorrhea. It is a common cause of primary amenorrhea.
**Option B:** Kallmann syndrome is a rare genetic disorder that affects the development of the olfactory system and the reproductive system, leading to hypogonadotropic hypogonadism and primary amenorrhea. It is a recognized cause of primary amenorrhea.
**Option D:** Rokitansky syndrome, also known as Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome, is a congenital disorder characterized by the absence or underdevelopment of the vagina and uterus, leading to primary amenorrhea. It is a common cause of primary amenorrhea.

**Clinical Pearl / High-Yield Fact**
It is essential to differentiate between primary and secondary amenorrhea, as their underlying causes and treatment options can be distinct. A thorough history and physical examination, along with relevant diagnostic tests, can help identify the underlying cause of amenorrhea.

**Correct Answer:**
✓ Correct Answer: C. Asherman's syndrome