Subreport Execution Sequence!!

Hi All!!!!

I am having one main report with 3 Sub reports on it. Its working fine..... I would like to know how the sub report queries are fired on database to get data, are they fired parallel or sequential?????

Example: Main Report contains 3 Sub-Reports A, B and C. Now when i run main report, what actually happens?

1. First main report query fired then Sub-report A then B then C.

OR

2. All the queries fired simultaneously.

Any help on this is good

Thanks & Regards,

Yash