The nucleus of an atom is usually made up of:
a. neutrons, which have no electrical charge.
b. protons, which a positive charge, and neutrons, which have no electrical charge.
c. protons, neutrons, and proteins that hold them together.
d. neutrinos, which have no electrical charge.
e. protons, which have a positive electrical charge, and proteins, which hold them together
Ans: b. protons, which a positive charge, and neutrons, which have no electrical charge.
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Which of the following is known to reduce nitrates to nitrites?
A. Calcium B. Zinc C. Potassium D. Iron
Opercula are
A. extensions of the body wall in polychaete worms. B. gill covers on a fish. C. internal spaces in a planarian used in digestion and respiration. D. gills on a lobster. E. tentacles on a hydra.
Why do things appear mainly black or white to us in low light?
A) Rods are more sensitive to light than are cones. B) Colored light does not strike the retina in low light. C) Only white light is available at night. D) Few action potentials are generated in low light. E) The diffused light of night does not fall on the fovea.
You are working in the field with your favorite bacteria species, Bacterium BB. You carry out some experiments with Bacterium BB, and find that it can now degrade toluene and it is pathogenic! What happened?
A. Bacterium BB was transformed with a resistance plasmid and a digestive plasmid. B. Bacterium BB acquired degradative and virulence plasmids by horizontal gene transfer. C. Bacterium BB was exposed to a bacteriophage which is now in its lytic phase. D. Bacterium BB sexually reproduced with another strain of bacteria that had both toluene-degrading gene and virulence gene. E. Bacterium BB picked up fertility and Col-plasmids via conjugation.