They are used to feel around and to capture prey. They extent their tentacles to capture prey, and use their nematocysts (nettle-like cells on their tentacles) to pierce and poison their prey. Hope that helps!
An organelle is a cellular structure which performs specific functions within a cell. Organelles are important to the cell as cells would not be able to function without them: even the most common organelle - the nucleus. A cell without a nucleus cannot function (except prokaryotes, as they have an undefined nucleus)
c. illustrate is your answer