In English, what factors influence the choice of verb form when a noun clause acts as the subject? Which of the following options are correct?

A、The entire content of the noun clause is considered as a single whole, so the verb is usually in the singular form.
B、If the noun clause contains a plural noun, the verb should be in the plural form.
C、In noun clauses introduced by 'what', the verb form is always singular.
D、When the subject of the noun clause is a specific noun within the clause, the verb form can vary according to the number of that noun.
E、When the noun clause acts as the subject, the verb form is always in the base form regardless of the content of the clause.