I believe this is a A. kernel sentence.
Kernel sentences are the most basic sentences in English language, meaning they are usually quite short, have a subject and a predicate, are active, indicative, and declarative.
The sentence John played his flute fits those descriptions. It has NP (John) + VP (played his flute). NP consists of one N (John), and VP consists of a V (played) and NP (his flute).
