I believe as you decompose an OO system x number of concepts develop which represent classes. A practical number of classes should be able to achieve both low coupling and high cohesion. With this train of thought responsibilities would be assigned relatively evenly across classes. Larmans video helped me understand this alot better
Yes you can mark and review questions. Be careful on marking too many questions though, the diagrams take up quite a bit of time. I also like to review my answers one last time before I click "FINISHED". Good Luck
Are there any comments about the whizlabs product from someone who has passed 141? I purchased whizlabs to pass the SCJP, which I heartedly recommend. Hopefully the XML whizlabs product is just as excellent a product.