**Core Concept**
The question is testing the understanding of the FIGO (International Federation of Gynecology and Obstetrics) staging system for cervical cancer, specifically the criteria for determining the clinical stage based on physical examination findings.

**Why the Correct Answer is Right**
In the FIGO staging system, the clinical stage is determined by the extent of tumor spread as assessed by physical examination. Parametrial involvement indicates that the tumor has spread to the tissues surrounding the cervix, and involvement of the lower 1/3 of the vagina indicates spread to the lower genital tract. The absence of a free space on the pelvic examination suggests that the tumor has spread to the pelvic sidewall or has caused obliteration of the pelvic cavity. Therefore, the correct stage for this clinical scenario is stage IIB, which is characterized by parametrial involvement and/or moderate to large tumor size that causes obliteration or narrowing of the pelvic cavity.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the clinical findings that correspond to stage IIB.
**Option B:** This option is incorrect because it does not accurately describe the clinical findings that correspond to stage IIB.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the FIGO staging system is primarily based on clinical examination findings, and imaging studies are not used for staging purposes.

**Correct Answer: C. Stage IIB.**