A classroom teacher posts three cards on which are written the words 'joyless,' 'careless,' and 'senseless.' The teacher goes through each word with students, guiding them to notice the repeated word part and what the meanings of the words have in common. As students encounter words that share similar qualities, they add them to a bulletin board. The activity best helps students decode unfamiliar words by teaching them to

While recognizing common roots is important, the focus of the activity is specifically on how affixes alter the meaning of the base words. The words presented to the students contain affixes that transform the meanings rather than relying solely on shared roots. Thus, this choice does not fully encapsulate the instructional goal.

This choice suggests a focus on etymology, which involves understanding the historical development of words. However, the teacher's activity centers on the functional use of affixes in modifying meanings rather than delving into the origins of the root words themselves. Therefore, this option does not accurately reflect the teaching strategy employed.

While using known definitions can aid in understanding new vocabulary, the activity primarily emphasizes the structural analysis of words with affixes. Students focus on the morphological aspects of the words rather than solely relying on previous definitions, making this choice less relevant to the teaching approach.