- AAB + BC + CD + DA = AC + BD
- BAB + BC + CD + DA > 2(AC + BD)
- CAB + BC + CD + DA < AC + BD
- DAB + BC + CD + DA < 2(AC + BD)
Step-by-Step Solution
Triangle OAB: AB < OA + OB; similarly BC < OB + OC, CD < OC + OD, DA < OD + OA. Adding: perimeter < 2(OA + OB + OC + OD) = 2(AC + BD).
Answer: D) AB + BC + CD + DA < 2(AC + BD)