Final answer:
Thelma Wilson is demonstrating formative assessment by gauging her kindergarteners' understanding of sounds and letters, and then deciding to move on to a new skill, which shows adaptive teaching.
Step-by-step explanation:
Thelma Wilson's actions in the classroom best illustrate the concept of formative assessment. By observing her kindergarteners' abilities in basic sounds and letter recognition, and after seeing them answer correctly, Thelma makes an informed decision to progress in the curriculum. This aligns with the educational practice where teachers gauge students' understanding through active participation and adjust their teaching strategies accordingly. Transitioning to another skill after students demonstrate understanding is a key element of adaptive teaching.