1、 "Best" Does Not Mean Ideal
It is very important to recognize that Sentence Correction questions ask for the best option of those given, not the best option in the universe. Indeed, often you will feel-andrighdy so-that all the answers, including the correct one, "sound bad." Correct GMAT Sentence Correction answers can sound very formal or awkward, so it is important to keep in mind that your task is to evaluate the given answer choices, not to create the ideal sentence. The ideal sentence often is not an option, and the right answer may sound rather wrong. To complicate matters, incorrect answer choices often sound right, Indeed, the GMAT exploits the fact that the English we hear is commonly riddled with grammatical mistakes.
(1) Subject-Verb Agreement 主谓一致
(2) Parallelism 平行
(3) Pronouns 代词(4) Modifiers 修饰语
(5) Verb Tense, Mood, & Voice 时态、虚拟语气和主被动语态
(6) Comparisons 比较
(7) Idioms. 习语/固定搭配