I think in the first two passage, we don't need to read the central sentence...what we should do is read it carefully and do the answer..but notice the pace...
in the last 2 passages, which will always appear after 20th questions, you can skip lots of sentence and read only the central sentence in case you don't have enough time..
siebel, I will take the test one day before you, ADD OIL TOGETHER!!HEHE....