To answer this question, you need to understand the order of transformations in a mapping for a flat file.
Option A) Expression transformation - This option is incorrect because the expression transformation is typically used to perform calculations or manipulate data within a mapping, but it is not directly related to the source transformation for a flat file.
Option B) Source qualifier - This option is correct. The source qualifier transformation is used to define the properties of the source data, such as the source table, columns, and filters. It is typically the first transformation to be used after the source transformation for a flat file.
Option C) Target transformation - This option is incorrect because the target transformation is used to define the properties of the target data, such as the target table and columns. It is typically used after the source qualifier transformation.
Option D) None of the above - This option is incorrect because the correct answer is B) Source qualifier.
The correct answer is B) Source qualifier. This option is correct because the source qualifier transformation is used immediately after the source transformation for a flat file in a mapping.