Suppose We Compare the Combined Mass of a C Atom

Multiple Choice

Suppose we compare the combined mass of a C atom and an O₂ molecule, both at rest, with the mass of a CO₂ molecule, also at rest. According to Einstein's theory, the combined mass of the C and O₂ is

A) slightly less, by an amount so small that it hard to measure, than the CO₂ molecule's mass.
B) considerably less than CO₂ molecule's mass.
C) considerably more than the CO₂ molecule's mass.
D) precisely equal to the CO₂ molecule's mass.
E) slightly more, by an amount so small that it hard to measure, than the CO₂ molecule's mass.