...if it rains on race day, and...
a) Race control decides to start the race with the SC in the lead...extreme wets are compulsary.
b) the rain starts within the last 3 minutes before race start and "a)" above does not happen...race control will delay the start of the race and allow teams to use any of the 2 wet tyre variants.
c) race control declares the track wet at any time before the race between the end of qualifying and "b)" above, and "a)" above does not happen...teams may use any wet tyre variant.
BUT no one is allowed to change suspension set ups.
"Fortunately I've got a bag with dry ice in [my suit], which I put next to my balls, so at least they stay nice and cool!"- Sebastian Vettel, 2009 Malaysian GP Friday Practice.