Option 1: Contaminate -> means to make impure or pollute, which is the opposite of purging/cleansing.
Option 2: Truncate -> means to shorten or cut off, unrelated to the concept of purification.
Option 3: Conceal -> means to hide or keep secret, not connected to cleansing or removal.
Option 4: Complicate -> means to make complex, irrelevant to purification or contamination.
Hence, Option 1: Contaminate -> PURGE means to cleanse, purify, or remove unwanted elements, while CONTAMINATE means to make impure or introduce pollutants—making them direct antonyms -> correct