A) NO CHANGE B) ameliorated C) gone down D) subsided

Before selecting the best option, it is crucial to comprehend the context in which the word will be used. However, since no context is provided in the exercise statement, the solution will presume that the student needs to understand the meaning of each word and how they could potentially be used in a proper context.

It's crucial to know the meaning of each of these options. Definitions are provided for A) NO CHANGE, B) ameliorated, C) gone down, and D) subsided: A) NO CHANGE - This option indicates that the current word in use should be kept, without any changes. No actual definition is provided since it just means to leave the word as it is. B) Ameliorated - This is a verb meaning "to make something better" or "to enhance." It is often used in the context of improving situations or conditions. C) Gone down - This can be taken as a phrase meaning "decreased" or "to have been reduced." It can be used for comparative purposes when discussing trends or changes. D) Subsided - This is a verb meaning "to become less intense, strong, or severe" or "to decrease in strength or intensity." It is commonly used when discussing the reduction of violent or negative events.

Since the context of the sentence or phrases is not available, it is not possible to advise which option to choose among A, B, C, or D. The student should analyze the sentence or passage where these options are to be inserted and identify the most appropriate word that fits the context and conveys the intended meaning. The choice will depend on the given context and how the word best fits the sentence or passage.