Which phonemic awareness activity involves the ability to isolate the initial sound of a word?

The activity that involves the ability to isolate the initial sound of a word is indeed sound isolation. This skill is crucial in phonemic awareness as it helps students recognize and manipulate the individual sounds within words. For instance, when children are asked to identify the first sound in a word like "cat," they would isolate the /k/ sound. This skill fosters improved decoding and spelling abilities as children learn to break words down into their sounds.

Other related activities serve different purposes in the realm of phonemic awareness. Word blending involves combining individual sounds or syllables to form words, which is not focused solely on isolating sounds. Sound segmentation is about breaking a word down into its constituent sounds but doesn’t primarily deal with isolating just the initial sound. Phoneme substitution requires changing one phoneme in a word to create a new word, which is more about manipulating sounds rather than just identifying a single initial sound. Therefore, sound isolation is specifically targeted at recognizing and pulling out the first sound of a word, making it the correct choice in this context.