The correct answer is - D. the insect touching the trigger hairs.
On this photos we have an example of an insect and a ''flesh-eating'' plant, where the insect is touching the trigger hairs of the plant's ''mouth'' and the plant quickly closes and traps the insect. All of the plants that have evolved to consume other living organism have a developed system that reacts on touch, so if an insect touches some of the parts of this system, usually a sticky liquid or hairs, it immediately reacts and closes, thus trapping the insect and starting to digest it.
