Answer: who
Step-by-step explanation:
A noun clause is characterized as the clause that functions as a subordinate clause in order to act as a noun(subject or an object) in the main/principal clause.
Since these clauses are subordinate, they begin with a conjunction i.e. subordinating in role. For example, whose, what, that, whether, etc.
These clauses usually replace a noun in order to play its role and can not convey an accomplished meaning in its own without the assistance of the main clause.