Different ____ (country) have different foods in the world.
公差d≠0的等差数列{an}的前n项和为Sn,若向量OA1→=ai,Siii=1,2,3,t为实数,若A1A2→=tA2A3→,则t=( )
看拼音,写句子。
yè wǎn ,wǒ zài yuàn zi lǐ shǔ xīng xing.