Final answer:
Externalities can be internalized through voluntary agreements as long as transaction costs are low relative to expected benefits.
Step-by-step explanation:
Externalities can be internalized through voluntary agreements as long as transaction costs are low relative to expected benefits. When transaction costs are high relative to expected benefits, it becomes more difficult to reach agreements that internalize externalities. Voluntary agreements can be either short-run or long-run agreements, depending on the specific context and duration of the agreement.