Answer:
D. Tighter federal oversight laws and restriction
Step-by-step explanation:
Positive externalizes refers to the things that is not directly involved in the exchange between consumers/producers, but will influence the market as a whole.
In the example above,
Public outcry toward the toxic dumping might encourage the government to make preventive measures on other areas. This can lead to the creation of Tighter federal oversight laws and restriction.
This will heavily benefit the market because the consumers would not experience the negative aspect for worsening environment from the products that they buy, and the producers could compete in a more healthy/humanly manner.