【单选题】Traditionally, college students hold a graduation ceremony to encourage themselves before they on their life jouney.
【单选题】According to the passage, how are ants guided by trail pheromones?
A.
They concentrate on the smell of food.
B.
They follow an ant who is familiar with the trail
C.
They avoid the vapor spaces by moving in a straight line.
D.
They sense the vapor through their antennae.
【单选题】Traditionally, college students hold a graduation ceremony to encourage themselves before they on their life journey.