Correct Response: C. There is a reciprocal relationship between spelling and phonics. The development of spelling and orthographic knowledge (e.g., doubling the final consonant of CVC words when adding an ending that begins with a vowel) reinforces the development of decoding skills. Similarly, students can utilize their phonics knowledge to build spelling skills. A and B are incorrect because phonics and spelling should be taught to all students systematically and concurrently, not simply in the context of an intervention. D is incorrect because irregular sight words are words that contain one or more elements that do not conform to regular phonics guidelines; thus, focusing on them would not reinforce phonics instruction.