In the periodic table, Silicon has an atomic mass listed as 28.08550 and not 28.00000. Choose the statement that explains why atomic masses in the periodic table are not integral numbers. 

• A. Samples are contaminated when masses are measured
• B. Atoms significantly change their masses due to gaining and losing electrons easily
• C. Masses are not exact.
• D. Exact measurements for small quantities are technically impossible.
• E. The weighted average of the isotopes is displayed as atomic mass.

Answer: (E)