Jellyfish are older than dinosaurs. In fact, having been around for some 500 million years, these alien-looking creatures are theoldest multicellular organisms on the planet. Jellyfish are famous for their deadly sting, and dozens of swimmers die every yearafter being stung by their poisonous tentacles. However, one variety of jellyfish could potentially offer huge benefits to humankind.
     Like all jellyfish, the Turritopsis dohrnii—a tiny species of jellyfish that was first discovered in the Mediterranean—beginslife as larvae before developing into polyps. In due course, these polyps spawn adult medusae, which are what we would recognizeas jellyfish. While other species of jellyfish ultimately die, the Turritopsis dohrnii has the unique ability to revert to its polyp phase.This process, known as transdifferentiation, can only happen if the creature is facing a physical or environmental threat. The polypsthen spawn more medusae, which are genetically identical to the original adult jellyfish. This process can be repeated endlessly. Itshould come as no surprise, then, that the Turritopsis dohrnii is more commonly known as the immortal jellyfish.
     Scientists have been intrigued by this exceptional ability since it was uncovered in 1996. Remarkably, according to NationalGeographic, the jellyfish’s cells can be completely transformed in the process. Muscle cells can turn into nerve cells, for instance.Dr. Stefano Piraino, an Italian biologist, hopes that studying the way jellyfish cells change could lead to possible cures for cancer.By looking into how jellyfish cells can regenerate into healthy ones, he expects that cancerous cells could be made to do the same.
     And if jellyfish can be immortal, could humans reverse the aging process, or perhaps even be immortal, too? The scientificconsensus at the moment is that it is not possible. However, if the immortal jellyfish can shed any light on ridding the world of ahorrible disease, then we’ll have a lot to thank this fascinating creature for.
31. According to the passage, which of the following orders shows the lifecycle of the immortal jellyfish?
(A) Medusae → polyps → larvae → medusae.
(B) Larvae → polyps → medusae → polyps.
(C) Polyps → larvae→ medusae→ polyps.
(D) Larvae → medusae→ polyps → larvae.