Which of the following statements is true?
electrons have a negative charge.
the n=1 shell can hold eight electrons.
the number of electrons in an atom is equal to the number of neutrons.
the second electron shell can hold 16 electrons.

What is histamine and what is its role in allergic reactions

Which blood cell spend most of their time in the lymphatic system?

What evidence supports the law of conservation of energy? a) mechanical energy is converted to chemical energy during photosynthesis. b) oxygen is made from the breakdown of carbon dioxide during photosynthesis. c)energy is absorbed by chlorophyll and becomes chemical energy during photosynthesis. d)the sun gives off light energy that is absorbed by plants.