例
uncle
Play tennis
1
aunt
Playing football
2
sister
Playing basketball
3
teacher
Playing ping-pong
4
mother
Playing volleyball
例:My uncle is playing tennis.
如图为不同浓度的生长素对植物不同器官的作用关系.请据图回答:
已知正方体ABCD-A1B1C1D1的棱长为a,AM→=12MC→,点N为BB1的中点,则MN→=( )