Sentence correction most often stifles non-native English speakers. In this style of question, a portion of or an entire sentence is underlined. The task is to decide if the underlined portion is correct or incorrect. If incorrect, choose the best possible replacement. Every question has five choices for the answer.
Errors tend to be obscure.
When they are, look for repetitions in the choices for the answer. One or two of the choices are a repeat the error. One or two others correct the initial error but create a new error. Non-native speakers often don't know grammar of their native language much less in English. Therefore, instructors should review the grammar of a sentence and the parts of speech.