**Core Concept**
Early detection of cervical cancer through screening can lead to its prevention or treatment at an early stage, thus reducing mortality rates. Cervical cancer screening typically involves Pap smear and/or human papillomavirus (HPV) testing to detect abnormal cell changes in the cervix.

**Why the Correct Answer is Right**
The correct answer is A. Ca cervix, as cervical cancer screening has been shown to reduce mortality rates through early detection and treatment of pre-cancerous lesions. This is achieved through regular Pap smear and/or HPV testing, which can identify abnormal cell changes before they progress to invasive cancer. The Pap smear detects abnormal cell changes, while HPV testing identifies the presence of high-risk HPV types that can cause cancer. Early detection and treatment of these lesions can prevent the development of invasive cervical cancer.

**Why Each Wrong Option is Incorrect**
**Option B:** Ca breast screening, such as mammography, can detect breast cancer at an early stage, but it cannot prevent the development of breast cancer. Screening for breast cancer is primarily focused on early detection, not prevention.
**Option C:** Ca prostate screening, including prostate-specific antigen (PSA) testing, can detect prostate cancer, but it is not effective in preventing its development. Prostate cancer screening is focused on early detection, not prevention.
**Option D:** Ca lung screening, such as low-dose computed tomography (LDCT), can detect lung cancer at an early stage, but it cannot prevent the development of lung cancer. Lung cancer screening is focused on early detection, not prevention.

**Clinical Pearl / High-Yield Fact**
The American Cancer Society recommends cervical cancer screening for women aged 21-65 years, with a Pap smear or HPV test every 3 years. Early detection and treatment of pre-cancerous lesions can prevent the development of invasive cervical cancer.

**✓ Correct Answer: A. Ca cervix**