Which sentence uses a colon correctly?

manatees need only a few things to survive up to age 60, enough food and to be left alone.

manatees need only a few things to survive: up to age 60 enough food and to be left alone.

manatees need only: a few things to survive up to age 60, enough food and to be left alone.

manatees need only a few things to survive up to age 60: enough food and to be left alone.

Which describes a difference between cephalopods and gastropods? cephalopods have a water vascular system, and gastropods have an open circulatory system. cephalopods live only in ocean environments, and gastropods live in a variety of environments. cephalopods have a simple nervous system, and gastropods have a complex nervous system. cephalopods are the largest group of mollusks, and gastropods are the smallest group of mollusks.