Re yesterday's Performance exam I actually thought the answer to the above question was the option involving Field limiting take off weight being a lot more/less (or whatever...) than Climb limiting. I think it may have been answer C. Either that or reduce a limiting VMCG...
As far as I could see...
Reduced thrust CAN be used on a wet runway as long as it is not considered contaminated. So it couldn't be that...
Trip fuel option just sounds wrong because that is not a reason to use it...the saving would probably be small and I have never seen that given as a reason to reduce take off thrust...
It will reduce the VMCG but as far as I'm aware there is no data to support that in the CAP 698 beyond the VMCG table for max thrust. I have heard of it being used as a technique in the real world but I'm just not sure whether it would be considered the right answer for the purposes of the exam...