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.
satellites that is a part of 15 years effort of subjecting the interactions of Earth’s atmosphere, oceans, and land surfaces
satellites, which is a part of a 15-year effort to subject how Earth’s atmosphere, oceans, and land surfaces interact
satellites, part of 15 years effort of subjecting how Earth’s atmosphere, oceans, and land surfaces are interacting
satellites that are part of an effort for 15 years that has subjected the interactions of Earth’s atmosphere, oceans, and land surfaces
satellites that are part of a 15-year effort to subject the interactions of Earth’s atmosphere, ocean, and land surface
1）请问D为什么不对？
2）在这个定语从句中，前面用are是为了和satellites一致，那么用part是因为后面的effort是不可数的吗？ | 
