托福阅读历年真题精选39_第2页

24. According to the passage, why do ants use different compounds as trail pheromones?

   (A) To reduce their sensitivity to some chemicals

   (B) To attract different types of ants

   (C) To protect their trail from other species

   (D) To indicate how far away the food is

25. 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

26. 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.

27. The word “furnish” in line 16 is closest in meaning to

   (A) include

   (B) provide

   (C) cover

   (D) select

28. The word “ oscillating “ in line 17 is closest in meaning to

   (A) falling

   (B) depositing

   (C) swinging

   (D) starting

29. According to the passage, the highest amount of pheromone vapor is found

   (A) in the receptors of the ants

   (B) just above the trail

   (C) in the source of food

   (D) under the soil along the trail