Like the rest of the Sterling GRE Biology prep books (see my other reviews on those books), I question the quality of this content. For example, on page 341, the answer explanation for #25 starts with, "Operons are only found in prokaryotes and encode for a cluster of related (i.e. similar function) genes." It has been established since the 1990s that operons may exist in eukaryotes (e.g. DOI 10.1093/bfgp/3.3.199). Operons aren't some obscure topic but a core topic in biology and this fact that they exist in eukaryotes isn't some obscure fact but prominently in the second paragraph on the Wikipedia page of operons.
With that said, I found this practice question book to be of much more value than the other Sterling GRE Biology prep books. There are about 300 pages of questions and 300 pages of answer explanations which were generally quite valuable (although some answer explanations seem to be copy-pasted from Wikipedia or some common source, without citation which is uncouth, and yet Sterling has the gall to stamp "Any duplication is illegal" annoyingly at the bottom of every page). Some of the answers had no explanations which was a bit annoying. In some cases, it makes sense since they are simply facts or self-evident, but some were less clear and I would have liked more explanations.
Overall, I found the Sterling GRE Biology prep books to be of questionable quality and value, with the one exception being this practice questions book. If I were to do it all over again, I would simply buy Campbell Biology, the Campbell Biology Study Guide (which has practice questions), and this practice questions book.