Final answer:
In Spanish, the noun 'mujer' is feminine while 'aquello', 'servidor', and 'rey' are masculine nouns.
Step-by-step explanation:
Out of the given nouns, 'mujer' is the only feminine noun. In Spanish, nouns have gender, and 'mujer' specifically refers to a female person. In contrast, 'aquello' (that), 'servidor' (server), and 'rey' (king) are all masculine nouns.
Learn more about Gender of nouns in Spanish