A خبر مرفوع (nominative predicate) is found in a nominal sentence (جملة اسمية), where it serves as the predicate of the subject (المبتدأ). Both the مبتدأ and the خبر are in the nominative case (مرفوع) by default.
Examining the options:
المعلمُ نشيطٌ - This is a nominal sentence. المعلمُ is the مبتدأ (subject, nominative) and نشيطٌ is the خبر مرفوع (predicate in the nominative case, marked by the damma/tanwin: ـٌ). This sentence contains a خبر مرفوع.
سافر محمد أمس - This is a verbal sentence (begins with the verb سافر). It has a فاعل (subject of the verb) but no خبر.
قرأ الطالبُ الدرسَ - This is a verbal sentence (begins with the verb قرأ). It has a فاعل and مفعول به, but no خبر.
اشترى الرجلُ كتابًا - This is a verbal sentence (begins with the verb اشترى). Again, فاعل and مفعول به, no خبر.
Only the first option is a nominal sentence containing a خبر مرفوع.
