The Science Museum is popular because people _____ do experiments there.
A:can
B:must
C:would
D:should
______ his pocket money, Bill bought many books for the poor children.
如图,△ABC是⊙o的内接三角形,AC=BC,D为 ⊙o中弧AB上一点,延长DA至点E,使CE=CD.(1)求证:AE=BD;(2)若AC⊥BC,求证:AD+BD=2CD.