ASP question from last ATPL sitting

[little-paddy]

Hi all,
Can anyone who took the May ASP ATPL exam remember the question regarding the straining of the fuel to check for contamination. It was something to do with when should you strain in order to be sure there are no impurities. The options were something like

Before each flight

After refuelling

Each morning


I can't remember the question for the life of me. Can anyone shed some light on it?

Thanks

L-P