Some diseases can be treated. Purple clothing can be made. Sea animals are not needed to make purple dye. Perkins is famous for discovering a new medicine.
I gave my students this multiple choice question: Many years ago, purple dye was made from some sea animals. Then, in 1856, William Perkins tried to make a new medicine. Instead, he found a way to make purple dye from coal. What is a positive effect of his discovery?

Only one answer is correct among these 4 choices:
- Some diseases can be treated.
- Purple clothing can be made.
- Sea animals are not needed to make purple dye.
- Perkins is famous for discovering a new medicine.

Could you tell me which one is correct?

Sea animals are not needed to make purple dye.