What is the role of the immune system’s first line of defense?

The crust of earth may a- continets and ocean floors. b-continents only. c-layers of sedimentary rocks and continents. d-all of the above

Match the following items. 1. high-intensity bundle of energy being emitted from some decaying nuclei gamma ray 2. particle radiating from the nucleus of some atoms beta particle 3. negative particle identical to an electron but radiating from a decaying nucleus alpha particle

Compare and contrast physical changes with chemical changes.