chipmunk: thank a lot for your suggestion, but i think that is just i am not familier with the reading . now all the thing that i have finished is only two sections of RC. i think do the reading can also do a great binifit for the background knowledges. So i will insist on doing the reading materials.
I'm afraid you can't go back to change your previous answers. For GMAT volcabulary, since you don't have much time, I'll suggest you to collect them during your reading.