Which excerpt best develops the central idea of the evolution of useful things.

Which two statements are true about a system? 1. a system is a group of objects analyzed as one unit. 2. energy that moves across system boundaries is conserved. 3. there’s only one way to define the boundaries of a system. 4. all systems are made by humans.

The number of brain synapses is believed to peak at

What kinds of antigens are found on the rbcs of a person with a+ blood