Hi. although you didn't underline anything in the presented words, when searching for your question on the internet, I was able to find another question exactly like yours, which showed that the last syllable of each presented word is underlined. In that case, I hope the answer below can help you.
Answer:
B horses
Step-by-step explanation:
As you can see in the question above, the words presented as an answer option have the last syllable completely identical to each other. However, the pronunciation of these syllables is different in one of these words and you can see this by slowly pronouncing them aloud. This way, you will notice that while the other words have the last syllable pronounced with a "z" sound, the word "horses" has the last syllable pronounced with an "s" sound.