I feel this.

This is a tricky one because of the specificity involved! We have to remember that according to the syllabus, ants of most species use pheromones - most but NOT all. This means that some ants species DO NOT use pheromones. C is about ants that only forage for food in the afternoon - if pheromones are ineffective at this time, why would they use them? Surely they must have a different method for collecting food to ensure survival. It follows that C is correct. E is a highly attractive incorrect answer choice but we don't know anything about the efficiency of ants that use pheromones versus those who do not. It would be wrong to assume that pheromone-using ants are more efficient only because the stimulus is about them.