A:However
B:On the other hand
C:At the same time
D:On the contrary
计算﹣5+4的结果是( )
∵AO⊥CO,
∴∠AOC=____(____).
又∵∠COD=40°(已知),
∴∠AOD=____.
∵∠BOC=∠AOD=50°(已知),
∴∠BOD=____,
∴____⊥____(____).