The universe began in an incredibly hot and dense state about 13.8 billion years ago. Since this time, it has been rapidly expanding, causing galaxies to move away from one another. Energy in the coldest depths of space can be explained as radiation left behind from the universe's early, more energetic state.

•there must be variation for the particular trait within a population.

•the variation must be inheritable (that is, it must be capable of being passed on from the parents to their offspring).

•individuals with one version of the trait must produce more offspring than those with a different version of the trait.good

explanation:

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.

b is the correct answer