Which can disrupt the cell cycle

cancer

Explanation:

Cancer can disrupt the cell cycle. Cancer is unchecked cell growth. Cell cycle is the process in which cells progress and divide. Mutations (random and sudden spontaneous changes) in genes can cause cancer by accelerating cell division rates or inhibiting normal controls on the system, such as cell cycle arrest or programmed cell death.

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.

well, i believe that the answer is 2. : 3