—Where's your father?
—He ______ Beijing. He _____there last month.
A:has gone to; went
B:has been to; went
C:has gone to; has gone
D:has been to; has gone
如图,已知∠AOB=60°,点P在边OA上,OP=10,点M,N在边OB上,PM=PN,点C为线段OP上任意一点,CD∥ON交PM、PN分别为D、E.若MN=3,则 CDDE 值为 ____ .
____<____<____<____<____.