**Core Concept**
The FIGO (International Federation of Gynecology and Obstetrics) staging system for cervical cancer is a widely used classification system that provides a uniform method for staging cervical cancer. The system takes into account the extent of tumor spread and is essential for determining prognosis and guiding treatment decisions.

**Why the Correct Answer is Right**
The FIGO staging system for cervical cancer primarily relies on clinical examination and diagnostic procedures, such as biopsy and colposcopy. It does not include specific imaging investigations like MRI, CT, or PET scans, which are not necessary for initial staging. The system focuses on the clinical assessment, including pelvic examination and biopsy results, to determine the extent of tumor spread.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while colposcopy is an essential diagnostic tool in the evaluation of cervical lesions, it is not considered a primary investigation for FIGO staging.
**Option B:** This option is incorrect because biopsy, including conization, is a crucial diagnostic procedure in the evaluation of cervical cancer, but it is not a separate investigation for FIGO staging.
**Option C:** This option is incorrect because imaging investigations like MRI, CT, or PET scans are not necessary for initial FIGO staging but may be used in further assessment and treatment planning.

**Clinical Pearl / High-Yield Fact**
Remember that the FIGO staging system for cervical cancer relies primarily on clinical examination and diagnostic procedures like biopsy and colposcopy, rather than imaging investigations.

**Correct Answer: A. Colposcopy**