gwd4-31新的问题

GWD6-Q39:

Twenty-two feet long and 10 feet in diameter, the AM-1 is one of the many new satellites that is a part of 15 years effort of subjecting the interactions of Earth’s atmosphere, oceans, and land surfaces to detailed scrutiny from space.

1. satellites that is a part of 15 years effort of subjecting the interactions of Earth’s atmosphere, oceans, and land surfaces

2. satellites, which is a part of a 15-year effort to subject how Earth’s atmosphere, oceans, and land surfaces interact

3. satellites, part of 15 years effort of subjecting how Earth’s atmosphere, oceans, and land surfaces are interacting

4. satellites that are part of an effort for 15 years that has subjected the interactions of Earth’s atmosphere, oceans, and land surfaces

5. satellites that are part of a 15-year effort to subject the interactions of Earth’s atmosphere, ocean, and land surfaces
                   

C选项为什么错啊？谢谢

 effort to do sth