To retrieve a maximum value in SQL, the user needs to know the appropriate keyword that retrieves the highest value from a column. The correct option is:

The Answer is: A

Option A: MAX is the correct keyword used to retrieve the maximum value from a column. It is an aggregate function in SQL that takes the column name as input and returns the highest value in that column.

Option B: TOP is a keyword used to limit the number of rows returned from an SQL query. It does not retrieve the maximum value from a column.

Option C: MOST is not a valid SQL keyword.

Option D: UPPER is a keyword used to convert a string to uppercase in SQL. It does not retrieve the maximum value from a column.