Answer:
There are no underlined nouns, but the nouns in the sentence are:
knight: common noun, concrete, countable
challenge: common noun, abstract, countable
King: proper noun
Arthur: proper noun
Step-by-step explanation:
A noun is a word that we use to name an object, person, animal, or place. There are common and proper nouns. We use the first ones to name objects or things, the second ones for places or people's names.
We classify common nouns into concrete when we can see and touch them and abstract when we cannot see them or touch them. Also, we classify them into countable and collective. Countable nouns are the ones that we can count, like pencils, apples, etc. Uncountable nouns are the ones that we cannot count, like rice or water. Collective nouns refer to a group of things, like an army.
A Knight is an object, so it is a common noun. We can see it and touch it, so it is concrete. We can count how many knights there are, which makes this noun countable.
Challenge is a thing we can not touch, so it is an abstract noun. We can count the challenges, so it is countable.
King, in this case, is a proper noun. It starts with a capital letter and refers to the title that this person has.
Arthur is a name, so it is a proper noun.