Which of the following are considered diphthongs?

Diphthongs are complex vowel sounds that begin with one vowel sound and glide into another within the same syllable, creating a single, distinct sound. The correct answer highlights a set of combinations that exemplify this characteristic.

The group identified correctly includes "oi" as in "boil," "oy" as in "boy," "ou" as in "out," and "ow" as in "cow." Each of these pairs represents a vowel glide where the sound shifts from one vowel to another within a syllable.

In contrast, the other choices consist largely of vowel pairs that do not feature the same gliding motion between vowel sounds or may represent individual sounds rather than creating a single new sound. For instance, "ai" in the first option forms a single vowel sound as does "ea," while in the other groups, pairs like "ee" and "ie" do not exhibit the diphthong's standard characteristic of gliding between two vowel sounds.

Understanding diphthongs is essential in phonics and language education, particularly in multi-sensory approaches, as it helps in decoding and spelling strategies in a structured way.