A is what you would do before C was added.
"steps" suggests another thing should be combined with C:
B states the obvious
D means tons of queries (so no)

Remember, the number of order is quite large over 10 million. Therefore, the best step to carry out is

1. Export in multiple batches: This implies that instead of trying to export the whole batch at once, which might not be possible it is best to export in fewer batches.

2. Use PK Chunking: This method involves the use of an automated system that reduces large orders into smaller chunks.