In a county, the new party and government leadership team has just been formed and is determined to do something practical for the masses. In the face of limited financial resources, the new leadership team made it clear that only two major tasks can be completed this year. For many of them included in the public policy agenda They believe that if you build a rural road, you cannot build a sewage treatment plant; if you build a sewage treatment plant, you need to build a sewage pipe; if you build a sewage pipe, you cannot build a garbage treatment plant. According to the thoughts of this leadership team, which of the following cannot be built at the same time this year? ['Country roads, sewage pipes.', 'Country roads, waste treatment plants.', 'Sewage treatment plant, sewage pipe.', 'Sewage treatment plant, garbage treatment plant.']