【单选题】

The author mentions the trail pheromone of the leafcutter ant in line 11 to point out
A．( how little pheromone is needed to mark a trail

B．( the different types of pheromones ants can produce
C．( a type of ant that is common in many parts of the world
D．( that certain ants can produce up to one milligram of pheromone