You are incorrect - our patient's acoustic events at the apex include a first heart sound, a second heart sound and a third heart sound (S3).
Your choice: S1 + S2 + fourth sound (S4)
This is a graphic example of a S1, S2 and an S4. The fourth heart sound occurs just before the first heart sound. It is low frequency and low intensity and usually reflects left atrial ejection of blood into a low compliance left ventricle.