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Box 1: Since you are looking for a specific pattern (PA followed by eight digits, e.g., PA 12345678), the best classification method is Sensitive Info Type. Sensitive Info Types allow pattern-based matching to identify structured data. Exact Data Match (EDM) is not needed because you're not comparing against a fixed dataset. Trainable classifier is not appropriate because this is a structured pattern, not an unstructured document classification.

Box 2: Since PA 12345678 follows a structured pattern, the most effective method is Regular Expression (Regex). A Regular Expression (Regex) can be written to match "PA" followed by exactly eight digits (e.g., PA\s\d{8}). Keyword dictionary is not ideal because it works for predefined words, not number patterns. Function is unnecessary because there is no need for checksum validation or predefined validation rules.