PMA stands for "Periodontal Disease Index," which is used to assess the periodontal health of individuals. It evaluates the presence and severity of periodontal disease by measuring clinical parameters such as probing depth and attachment loss. The other options do not correspond to the PMA acronym.

The most common aetiology of oral cancer in India is tobacco products (Answer: 2). The high prevalence of tobacco use, particularly in the form of betel quid with tobacco, paan masala, and other smokeless tobacco products, significantly increases the risk of developing oral cancer.

Patient records, including dental X-ray films, are typically the property of the dentist who created them. The dentist is responsible for maintaining, storing, and safeguarding these records according to legal and professional standards. However, patients do have the right to access and obtain copies of their records.

The OHI-S (Oral Hygiene Index-Simplified) is a clinical index developed to assess oral hygiene status by measuring the amount of oral debris and calculus present on the teeth. It provides a simple and effective way to evaluate the cleanliness of the mouth and is widely used in dental research and practice.

Standard deviation is a statistical measure that quantifies the amount of variation or dispersion in a set of values. It is not a measure of central tendency or correlation.