Select the most appropriate option to fill in the blank.

He claims to be the ______ kid in the school.

smartest

The correct option to fill in the blank is smartest.

The sentence is about the boy claiming to be the smartest kid in the school. The word "smartest" is the superlative form of the adjective "smart," which means intelligent or clever. It is the most appropriate word to use in this context, as it conveys the meaning of the boy being the most intelligent or clever kid in the school.

The other options are not as appropriate.

• Smartness is a noun that refers to the quality of being smart. This is not the right word to use in this context, as it does not make sense to say that the boy claims to be the smartness kid in the school.
• Smarting is a verb that means to feel pain or discomfort. This is not the right word to use in this context, as it does not make sense to say that the boy claims to be the smarting kid in the school.
• Smarter is the comparative form of the adjective "smart." This is not the right word to use in this context, as the boy is claiming to be the smartest kid in the school, not just smarter than other kids.