High-frequency words are important because they:

High-frequency words are indeed crucial in developing reading skills, primarily because they appear often in various texts and contribute significantly to reading fluency. These words, which include common terms such as "the," "and," "is," and "to," make up a large percentage of the words found in children's literature and everyday reading materials.

Familiarity with high-frequency words allows young readers to recognize them quickly, which helps reduce the cognitive load while reading. This quick recognition enables students to focus more on comprehension and meaning rather than getting bogged down by deciphering every single word. As students become more fluent in reading high-frequency words, their overall reading speed and comprehension improve, fostering a more enjoyable and effective reading experience.

In contrast, the other options do not reflect the essential role these words play in literacy. For instance, high-frequency words are not necessarily the longest, nor are they exclusive to academic writing. While improving spelling skills is beneficial, the primary function of high-frequency words is to enhance fluency and comprehension in reading, making the third choice the most accurate.