A:5,10,15,20,25
B:5,12,31,39,57
C:5,15,25,35,45
D:5,17,29,41,53
---Where ______ you yesterday morning?
---I ______ at my uncle's home.
已知平行四边形ABCD中,AC为一条对角线,若AB→=(2,4),AC→=(1,3),则AD→·BD→=( )