All three options can cause tsunamis:
I. Earthquake - Yes, underwater earthquakes are the most common cause of tsunamis.
II. Volcanic eruptions - Yes, volcanic eruptions, especially those that cause large-scale collapses or eruptions that displace water, can generate tsunamis.
III. Landslides - Yes, both underwater and coastal landslides can displace enough water to generate tsunamis.
So, the answer is that all three (I, II, and III) can cause tsunamis.