An informal reading inventory is used to determine what aspect of a student's abilities?

An informal reading inventory primarily assesses a student's reading abilities in various areas, particularly focusing on their comprehension of narrative text. This type of inventory often involves reading passages and answering questions about them, allowing educators to gauge a student's understanding of the text. Through these assessments, teachers can identify specific strengths and weaknesses in a student's comprehension skills, which is crucial for tailoring instruction to meet individual needs.

In contrast, the other options pertain to different aspects of reading that an informal reading inventory may not specifically target. Vocabulary complexity could be assessed through other means, such as tests designed to evaluate vocabulary knowledge directly, rather than through informal reading assessments. Listening capacity is generally not the focus of a reading inventory since it emphasizes the reading process itself and comprehension of the material read. While fluency in oral reading is important and sometimes touched upon in informal assessments, it is distinct from the comprehension focus that reveals how well a student understands narratives and texts.