Answer:
The correct choice is:
Human activities on land.
The passage of key information here suggests that the vast majority of pollutants in the oceans come from human activities that take place on land.
The other choices are not supported:
• Boats - Boats are a means of transporting things on/over the oceans, but they are not themselves the primary source of pollution. Pollution comes from spills, discharges, and accidents involving boats, but boats alone do not introduce the most pollutants.
• Oil tanker spills. - While oil tanker spills can be highly damaging, they are not responsible for introducing the bulk of pollutants into the oceans. There are many other types of pollutants and they come from a wide range of land-based human activities.
• Underground storage facilities. - There is no information in the context provided to support this as a major source of ocean pollution.
So based on the context, the correct choice is "Human activities on land."
Step-by-step explanation: