We know that there are 4 styles of gender nouns, let’s examine their usage-
1)Feminine gender noun- it's accustomed indicate girls, women, and feminine animals.
Example- Goddess, maiden, lioness, etc.
2)Masculine gender noun- it's accustomed indicate boys, men, and male animals.
Example- God, maid-servant, lion, etc.
3)Common gender noun- it's wont to indicate nouns which will either be female or male.
Example- Cook, doctor, teacher, etc.
4)Neuter gender noun- it's wont to indicate nouns that are neither female nor male.
Example- Book, chair, car, etc.
There are three nouns within the above question; Empress, subjects, and humility.
Now, let’s study the given options-
a)Empress- it's the female gender noun of the emperor. Hence, it's the proper option.
b)Subjects- it's a noun because it includes the gathering of citizens of an empire as an entire. Hence, it's an incorrect option.
c)Lesson- it's a neutral gender noun because it denotes a gender-less concept. Hence, it's an incorrect option.
The correct answer is Option ‘a’.