Answer:
B) I do not know when the flagpole was painted is the correct answer.
Step-by-step explanation:
A noun clause is a dependent clause that has the role of a noun. To indicate these clauses, there are several words such as that, whatever, how, when, among others. An adverb is a word that describes an adjective, a verb, or even other adverbs. There are different types, like frequency adverbs, adverbs of manner, and adverbs of time.
In the second option, the introductory word to the noun clause is when, but it also acts as an adverb (even if it is unknown or not accurate)because it modifies the noun clause, which is "the flagpole was painted".