The rule with Sentence Equivalence is that the two answers must be synonyms, i.e. very similar words.
With this in mind try the question below.
As we age, our political leanings tend to become less ________; the once dyed-in-wool conservative can betray liberal leanings, and the staunch progressive may suddenly embrace conservative policies.
(A) demanding
(B) extreme
(C) pronounced
(D) biased
(E) conspicuous
(F) obtuse

How to Solve It!

So the perfect word in this case is extreme. It even goes together with the word political. But does that mean extreme is one of the answers? Only if there is another word that is a synonym with extreme. Alas, there is none.
Or maybe you thought that biased was an even better answer. Again, the word seems to fit the political context. But are biased and extreme synonyms? They are not. Does biased have a synonym amongst the remaining answer choices? Again, no.
So, even though extreme and biased both worked independently neither of them is the answer (and now you see why many are afraid to take the new GRE).
One option, then, is to basically ignore the sentence and find a pair of synonyms. This method was one I espoused earlier, with one condition: that you have a strong vocabulary. So let’s say you do. In this sentence there is only one pair of synonyms: conspicuous and pronounced. Both are synonyms for marked/obvious. When you plug that back into the sentence, it makes sense–as we age our political tendencies become less obvious.
Notice, too, how the sentence talks about how as people age their political leanings take on aspects of the opposing sides. If you pick up on this, you can also arrive at the answer, without necessarily having a strong vocabulary.
Takeaway
All in all, this was a toughie. But remember, tread lightly on Sentence Equivalence. Don’t just dive into the answer choices and grab onto the word that sounds the best. Sometimes, what appears perfect can be a trap.