Sorry to bust your bubble but no matter how much you do prepare (sample papers) you will most likely not do that grate, 30% if you are lucky. Most of the guys who do it are uni grads, ages ranging from 21-30 who 9 times out of 10 do pretty well.
Do still go ahead with it but don't be set on one...
Yeah it's D cause that's the only one that has the ratio of 10:1
The question didn't state which is primary and which is secondary but I guess you just have to assume