Which of the following is an example of a consonant digraph?

A consonant digraph is a combination of two consonant letters that produce one sound or phoneme. The correct example from the given options is the combination of letters represented by "ch" in the word "chair."

"Ch," "sh," and "th" are all examples of consonant digraphs as well, as they also consist of two letters that together form a single sound. The combination "ck," as seen in the word "back," does not constitute a digraph because it represents two distinct sounds; "c" and "k" are pronounced separately. Therefore, it does not align with the definition of a digraph.

In summary, "ch," "sh," and "th" each create unique sounds with their combinations, whereas "ck" does not meet that criterion, making "ch" the correct choice as it exemplifies what a consonant digraph should be.