**Core Concept**
Irregular and infrequent menstruation refers to a condition where the menstrual cycle is not regular, and the intervals between periods are inconsistent, often resulting in fewer than 8-9 periods per year. This condition is associated with hormonal imbalances, particularly related to the hypothalamic-pituitary-ovarian axis.

**Why the Correct Answer is Right**
The correct term for irregular and infrequent menstruation is **Oligomenorrhea**. This condition is characterized by a decrease in the frequency of menstrual periods, often due to anovulatory cycles or hormonal imbalances. It can be caused by various factors, including polycystic ovary syndrome (PCOS), thyroid disorders, and excessive physical activity.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because **Polyuria** refers to the production of an abnormally large volume of urine, typically seen in diabetes insipidus or diabetes mellitus. It is not related to menstrual irregularities.
**Option B:** This option is incorrect because **Dysmenorrhea** refers to painful menstruation, which is a different condition from irregular and infrequent menstruation.
**Option C:** This option is incorrect because **Menorrhagia** refers to abnormally heavy or prolonged menstrual bleeding, which is also a different condition from irregular and infrequent menstruation.

**Clinical Pearl / High-Yield Fact**
Oligomenorrhea is often associated with an increased risk of endometrial hyperplasia and cancer due to prolonged exposure to unopposed estrogen.

**Correct Answer: C. Oligomenorrhea**