Silicon, which makes up about 25% of Earth's crust by mass, is used widely in the modern electronics industry. It has three naturally occurring isotopes, 28-Si, 29-Si, and 30-Si. Calculate the atomic mass of silicon.
A. 29.2252 amu B. 28.9757 amu C. 28.7260 amu D. 28.0855 amu E. 27.9801 amu