What characteristic is typical of spondee words?

Spondee words are characterized by having two syllables that are produced with equal stress. This means that both syllables of the word are emphasized in the same manner, which is essential for specific assessments in speech-language pathology, particularly when evaluating speech perception and production. The equal stress on both syllables helps clinicians understand the individual's ability to process and produce speech sounds effectively, as well as to assess their articulatory precision.

The other choices do not accurately capture the defining feature of spondee words. For instance, while some two-syllable words may indeed be phonetically balanced, this characteristic applies broadly and does not specifically pertain to spondees. Also, monosyllabic words are not relevant in this context, as spondees consist exclusively of two syllables. Furthermore, the claim that spondee words represent a selection of common English words does not define their nature; it is the stress pattern that is the defining characteristic. Therefore, the emphasis on equal stress makes option D the correct explanation of spondee words.