These specialized beaks are perfectly adapted for reaching deep inside long, tubular flowers to sip or suck the nectar. This adaptation allows them to access a food source that many other birds and insects cannot reach, making them important pollinators. An example of bird which possesses such feature is the sun bird.

A. tearing: Tearing is typically associated with birds of prey (raptors) which have sharp, hooked beaks for ripping flesh.

B. sieving: Sieving is a feeding method used by birds like ducks, which use specialized beaks to filter small food items from water or mud.

C. boring: Boring (drilling) is done by birds like woodpeckers, which have strong, chisel-like beaks to make holes in wood for insects or nests.

The correct answer is option D - sucking