The short answer is yes. You can return to any question within a section. The real question is, how does this inform your strategy?
One camp says that unless you have plenty of time remaining, which most won’t, you should work through each question as efficiently as possible without planning to return. If you don’t know an answer, guess and move on.
Another camp recommends trying to get as many questions right as possible. If a question looks too difficult skip the question. Spending too much time on any one question will eat up the time you could be spending on an easier question. If time permits, return to the more difficult question.
Somewhere in the Middle
Both can be valid strategies, but ultimately, the answer depends on the test taker. Regardless, most often the truth lies somewhere between the two camps mentioned above. Below are a few important factors to keep in minding when deciding whether to leave a question unanswered.
The Power of Recognition
Our brains work in interesting ways. A solution that seems increasingly elusive the longer you stare at a problem can suddenly appear when you return to the problem later. Of course, this doesn’t always work, but whether you are dealing with a byzantine text completion or a cryptically-phrased math question, the solution is more likely to appear when you see the problem a second time. The caveat is you must look at the problem first and try to understand it, instead of just thinking, “oh that looks hard, I’ll come back later and maybe it’ll look easy”.
The 45-second Rule
If the pathway to a solution doesn’t present itself within 45 seconds, you may be better off returning to the question later. The number doesn’t have to be exactly 45-seconds, but that is generally enough time to determine whether to move on.
Answer Question But Return to It Later
One strategy is to always answer a question even if you have no idea what the answer is. If that’s the case, just make sure to flag the question so you can return to it later.
Practice Makes Perfect
Practice on the Revised GRE Test CD until you find a strategy that works best for you. This process will allow you to get a sense of the types of questions that you should immediately skip and those you should spend a little more time trying to get right the first time.
Since you can return to a question on the GRE, it simply becomes a question of the right strategy for each individual test taker. Practice until you find the right strategy for you to employ on test day.