There are an extremely large number of antsworldwide. Each individual (个体的) ant hardly weigh anything, but put together they weigh roughly the same as all of mankind. They also live nearly everywhere, except on frozen mountain tops and around the poles.Foranimals their size, ants have been astonishingly successful, largely due to their wonderfulsocial behavior.
In colonies (群体) that range in size from a few hundred to tens of millions, they organize their lives with a clear division of labor. Even more amazing is how they achievethis level of organization. Where we use sound and sight to communicate, ants dependprimarily on pheromone (外激素), chemicals sent out by individuals and smelled or tastedby fellow members of their colony. When an ant finds food, it produces a pheromone that will lead others straight to where the food is. When an individual ant comes under attack or is dying, it sends out an alarm pheromone to warn the colony to prepare for a conflict as a defense unit.
In fact, when it comes to the art of war, ants have no equal. They are completely fearless and will readily take on a creature much larger than themselves, attacking in large groups and overcoming their target. Such is their devotion to the common good of the colony that not only soldier ants but also worker ants will sacrifice their lives to help defeat an enemy.
Behaving in this selfless and devoted manner, these little creatures have survived on Earth, for more than 140 million years, far longer than dinosaurs. Because they think as one, they have a collective (集体的) intelligence greater than you would expect from itsindividual parts.
21.We can learn from the passage that ants are ____________.
A. not willing to share food
B. not found around the poles
C. more successful than all other animals
D. too many to achieve any level of organization
22.Ants can use pheromones for______.
A. escape B. communication C. warning enemies D. arranging labor
23.What does the underlined expression "take on" in Paragraph 3 mean?
A. Accept. B. Employ. C. Play with. D. Fight against.
24.Which of the following contributes most to the survival of ants?
A. Their behavior. B. Their size. C. Their number. D. Their weight