If the italicized part of the sentence is the word <em>courses, </em>then the correct answer is predicate noun/nominative.
A predicate nominative is the first noun found after a linking verb, such as to be, or in this sentence, the verb <em>are. </em>You can see that the first noun following the verb <em>are </em>is the word <em>courses, </em>which means it is a predicate nominative.
Answer:
relating to a transitional or initial stage of a process
Your answer here is D. watches, worries
Is - two billion dollars is a unit, one unit so it is singular and you use the singular verb
think - scientists is a plural, therefore, you must use the plural verb form of think