Final answer:
3. Submarine landslides can trigger tsunamis, and tsunamis can trigger submarine landslides. However, submarine landslides and tsunamis are not always directly related.
Step-by-step explanation:
Submarine landslides can trigger tsunamis. When a large mass of sediment on the seafloor becomes unstable and slides down the slope, it can displace a significant amount of water, resulting in a tsunami.
Tsunamis can trigger submarine landslides as well. The immense energy of a tsunami wave hitting the seafloor can cause the sediment to become unstable and slide downhill.
Therefore, it is not true that submarine landslides and tsunamis are unrelated phenomena, as stated in statement 3. However, it is not always the case that submarine landslides and tsunamis occur together, as stated in statement 4.