Two rule boxes head the page, one for a before a consonant sound and one for an before a vowel sound, and ten sentences follow with a box in each waiting for the article. This is the sheet where the skill stops being about single words and starts being about writing.
The rule is stated in terms of sound rather than letter, which is the version that keeps working later when a child meets an hour and a unicorn. Sentence two is the quiet test of the set: an old teddy bear takes its article from old, not from teddy, and a child who has only ever chosen articles for single nouns usually pauses there. The other nine stay straightforward so that one has room to land.