Reading Instruction Competence Assessment (RICA) Practice Test

A diphthong is a complex vowel sound that begins with one vowel sound and glides into another within the same syllable. The example "ow" illustrates this concept effectively, as it begins with the vowel sound /a/ and glides into the vowel sound /ʊ/. This combination creates a single distinct sound, making "ow" a classic example of a diphthong. In contrast, the other options presented do not exemplify diphthongs. "Sh" and "Ch" represent consonant sounds rather than vowel combinations, which are essential to identifying diphthongs. Meanwhile, "Ph" is also a consonant digraph that represents a single consonant sound, /f/, and does not contain any vowel sounds at all. Thus, "ow" stands out as the correct option that defines a diphthong.