making cars run on less fuel finding more sites for copper mines making ocean liners bigger and faster replacing human workers with robots
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Of these research projects, which is the best choice for a student who is interested in environmental issues to study?
Possibilities:
- making cars run on less fuel
- finding more sites for copper mines
- making ocean liners bigger and faster
- replacing human workers with robots

making cars run on less fuel