To answer this question, we need to understand the different execution modes in Datastage 8.5 and their implications.
A. Combinability mode - This mode allows the XML stage to combine the data from multiple partitions into a single output file. However, in Datastage 8.5, the XML stage does not support the combinability mode.
B. Parallel mode - This mode allows for parallel processing of data across multiple partitions. However, it does not address the requirement of creating a single XML document with data from multiple partitions.
C. Impersonation mode - This mode is not directly related to the requirement of creating a single XML document with data from multiple partitions.
D. Sequential mode - This mode processes the data sequentially, meaning it processes one partition at a time. In this mode, the XML stage can be used to create a single XML document with data from multiple partitions. Therefore, the correct answer is D.
The correct answer is D.