Answer:
- S - Subject.
Step-by-step explanation:
A noun clause is elucidated as the cluster of words functioning as a noun in the sentence. These clauses can function multi-purposely as subjects, indirect or direct objects, subject compliment, etc. and are usually subordinate as they begin with relative pronouns like 'when, whom, which, etc. or its expanded forms like whichever, whatever, whomsoever, etc.
In the given sentence, the noun clause 'What I had been hoping for' is functioning as a subject as it is acting upon the verb('was') in the sentence. However, the clause is dependent on the latter part(predicate) of the sentence to accomplish its meaning yet it demonstrates the key idea(subject) that is being discussed in the sentence.