When a singular noun has an accent mark on the last syllable, you should leave it as is. The Option B is correct.
An accent marks which is also known as diacritics or tilde marks serve an essential role in the Spanish language by indicating the stress or emphasis of a word. When a singular noun has an accent mark on the last syllable, it show that the stress falls on that final syllable and this stress pattern remains unchanged in its singular form.
So, the accent mark is retained to guide correct pronunciation. For example, the word "café" (coffee) has an accent mark on the last syllable, and in its plural form, "cafés," the accent mark remains in place to indicate that the stress still falls on the last syllable.