If M is the atomic mass and A is the mass number the packeing fraction is given by

Options

A. `A/(M-A)`
B. `(A-M)/A`
C. `M/(M-A)`
D. `(M-A)/A`

Explanation

To find the packing fraction given the atomic mass (M) and mass number (A), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Mass Number and Atomic Mass**:
- The mass number (A) is the total number of protons and neutrons in the nucleus of an atom.
- The atomic mass (M) is the actual mass of an atom, which is usually slightly less than the mass number due to the binding energy that holds the nucleus together.

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