The car accident happened ____ a cold winter morning. Luckily, no one was hurt.
A:in
B:on
C:at
D:of
伊核问题、阿富汗向题、乌克兰危机…,过去的一年世界并不太平,中国作为负责任的大国积极参与并推动相关问题的解决。这说明( )
25+40=____
32+30=____
50+36=____
5+43=____