Under the MSBOC Highway classification, which of the following statements about airport runway work is correct?

1. Airport runway construction is outside every Mississippi contractor classification
2. Highway is the Mississippi trade classification whose scope includes airport runway construction, in addition to roads, highways, bridges, excavation, and grading
3. Only the Residential Roofer classification may pave airport runways
4. Airport runways may be built without compaction or smoothness control because aircraft loads are lighter than trucks