(Refer to Figure 1.) Class A = 18,000 ft MSL; Class G (nontowered airport with instrument approach) =14,500 ft MSL, 1,200 ft AGL and 700 ft AGL. Class B, Class C, Class D and Class E are undesignated. Which altitude is the normal upper limit for Class D airspace? Group of answer choices 2,500 feet AGL 1,000 feet AGL 4,000 feet AGL