Which of the following illustrates the concept of 'letter combinations'?

The concept of 'letter combinations' refers to pairs or groups of letters that, when placed together, create distinct sounds or phonemes in words. The letters 'ou' serve as a clear example of a letter combination because they work together to produce a specific sound, as heard in words like "house" or "cloud." This illustrates how multiple letters can combine to create unique pronunciations that are essential for phonics and reading development.

In contrast, a single letter like 'a' does not represent a combination of letters. Similarly, the word 'cat' consists of individual letters rather than a combination, and the syllable 'ta' does not illustrate the combination of two or more letters either. The focus on multiple letters working together to create a specific sound is what makes 'ou' the correct representation of the concept of letter combinations.