Final answer:
To confirm the student's difficulty in decoding words, the teacher should administer a phonemic-awareness assessment where the student breaks down spoken words into individual phonemes.
Step-by-step explanation:
A first-grade teacher who notices a student has difficulty decoding words like 'ran,' 'pet,' 'him,' and 'hot' is seeking the best way to confirm the student's difficulty. Among the options provided, administering a phonemic-awareness assessment in which the student breaks spoken words into individual phonemes (Option A) would be the most appropriate method. This approach specifically targets the fundamental skills of phonemic awareness that are essential for decoding and would provide the teacher with clear insight into the student's understanding and ability to manipulate the individual sounds in words.