Q: Q: Isotopes have the same number of protons and electrons, but a different number of what? Choices: - reactions - impurities - atoms - neutrons A:
A: neutrons

Q: Q: Sickle-cell disease significantly impairs the function of what? Choices: - limbic system - nervous system - metabolism system - circulatory system A:
A: circulatory system

Q: Q: Blood enters the heart in what valve? Choices: - tricuspid - aortic - mitral - atria A:
A: atria

Q: Q: Most radioactive emissions that people are exposed to are on the order of a few dozen what? Choices: - ticks - micrograms - millivolts - millirems A:
A: millirems