Correct Answer: Brunette

Solution : The correct choice is the second option.

Brunette is a term used to describe a person, especially a woman, with brown hair. It specifically refers to the hair colour, making it an appropriate substitute for the given group of words.

The meanings of the other words are:

• Blunt: It means having a dull edge or point; not sharp. It can also refer to a direct manner of speaking, lacking subtlety.
• Blonde : It means having fair or light-coloured hair, often used to describe women with light hair shades.
• Bumble: It denotes moving or acting clumsily or awkwardly. It can also refer to a continuous, humming noise or the act of buzzing like a bee.

Therefore, the right answer is brunette.