The Venus flytrap counts the number of times its trigger hairs are touched before closing the trap.
Why it is true
This carnivorous plant requires at least two touches within a short time frame to close, an evolutionary mechanism that prevents wasting energy on false alarms, such as raindrops or debris.
Source: Botany
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.