**Core Concept**
The maturation index is a cytological parameter used to assess the hormonal influences on the female reproductive system. It is a ratio of the different types of cells present in a cervical smear, reflecting the balance between estrogen and progesterone levels.

**Why the Correct Answer is Right**
A maturation index of 100/0/0 indicates a predominance of parabasal cells, which is a sign of an estrogen-deficient state. This is typically seen in postmenopausal women or in cases of estrogen deficiency due to hypogonadism or ovarian failure. The absence of intermediate and superficial cells suggests that the cervical epithelium is not being stimulated by estrogen, leading to an arrest in cellular maturation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately reflect the cytological characteristics of a maturation index.
**Option B:** This option is incorrect because it implies a different cellular composition, which is not consistent with a 100/0/0 maturation index.
**Option C:** This option is incorrect because it is not a valid interpretation of the maturation index.

**Clinical Pearl / High-Yield Fact**
A maturation index of 100/0/0 is a red flag for estrogen deficiency, which may be due to various underlying causes, including ovarian failure, hypogonadism, or exogenous estrogen therapy.

**Correct Answer: D. Estrogen deficiency**