Answer: in sentence 3, the underlined phrase "the students" is an indirect object.
Explanation: an indirect object is a noun phrase referring to someone or something that is affected by the action of a transitive verb (typically as a recipient), but is not the primary object. In the first sentence, the underlined phrase is "the subjects" which is the direct object, in the second sentence the underlined phrase is "the notes" which is also the direct object, and in the third sentence the underlined phrase "the students" is an indirect object (because it represents a recipient).
