**Core Concept**
Primary amenorrhoea refers to the failure to initiate menstruation by the age of 16 years in the presence of normal secondary sexual characteristics. It is a complex condition with various underlying causes, including genetic, anatomical, and hormonal abnormalities.

**Why the Correct Answer is Right**
Stein-Leventhal syndrome, also known as Polycystic Ovary Syndrome (PCOS), is a common endocrine disorder characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovarian morphology. Unlike other options, PCOS typically presents with secondary amenorrhoea, not primary amenorrhoea. Secondary amenorrhoea is defined as the cessation of menstruation for 3 months or longer in a woman who has previously menstruated.

**Why Each Wrong Option is Incorrect**
**Option A:** Turner's syndrome is a chromosomal abnormality characterized by the complete or partial absence of one X chromosome, leading to ovarian dysgenesis and primary amenorrhoea. Therefore, Turner's syndrome is a correct association with primary amenorrhoea.
**Option C:** Rokitansky-Kustner-Hauser syndrome, also known as Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome, is a rare congenital disorder characterized by the absence or underdevelopment of the vagina and uterus, leading to primary amenorrhoea. Thus, MRKH syndrome is a correct association with primary amenorrhoea.
**Option D:** Kallmann syndrome is a rare genetic disorder characterized by delayed or absent puberty, including primary amenorrhoea, due to hypogonadotropic hypogonadism. Therefore, Kallmann syndrome is a correct association with primary amenorrhoea.

**Clinical Pearl / High-Yield Fact**
It is essential to note that primary amenorrhoea requires a thorough evaluation to identify the underlying cause, including genetic, anatomical, and hormonal abnormalities. A detailed history, physical examination, and diagnostic tests, such as karyotyping and pelvic ultrasound, are crucial in determining the underlying cause of primary amenorrhoea.

**✓ Correct Answer: B. Stein-Leventhal syndrome**