Answer: The sentence that uses a noun clause to combine the ideas provided is A. We know most about what interests us.
Explanation: A noun clause is a dependent clause, which means it cannot stand alone as a sentence because it does not express a full idea. Noun clauses act as nouns and they are generally introduced by words such as "what", "why", "how" and "where". In sentence A. ("We know most about what interests us"), "what interests us" is a noun clause since it has been introduced by "what", it is acting as a noun and it cannot stand alone as a sentence. Moreover, its function in the sentence is object of the preposition ("about").
