Which of these are a pair of Isotones and Isobars?

Options

A. `""_(20)^(40)Ca & ""_(19)^(39)K`
B. `""_(6)^(12)C & ""_(8)^(16)O`
C. `""_(20)^(40)Ca & ""_(18)^(40)Ar`
D. `""_(29)^(65)Cu & ""_(30)^(65)Zn`

Explanation

To determine which pairs of elements are isotones and isobars, we need to understand the definitions and then apply them to the given pairs.

### Definitions:
1. **Isotones**: Atoms that have the same number of neutrons but different atomic numbers.
2. **Isobars**: Atoms that have the same atomic mass (total number of protons and neutrons) but different atomic numbers.

### Step-by-Step Solution:

**Step 1: Identify the Atomic Mass and Atomic Number**
- For each pair of elements, identify their atomic mass (A) and atomic number (Z).

**Step 2: Calculate the Number of Neutrons**
- Use the formula: Number of Neutrons (N) = Atomic Mass (A) - Atomic Number (Z).

**Step 3: Check for Isotones**
- Compare the number of neutrons (N) for each pair. If they are the same, then the pair is classified as isotones.

**Step 4: Check for Isobars**
- Compare the atomic mass (A) for each pair. If they are the same, then the pair is classified as isobars.

**Step 5: Analyze Each Pair**
- Go through each option provided in the question and apply the above steps to determine if they are isotones, isobars, or neither.

### Example Analysis:
Assuming we have pairs like (A, Z):
1. Pair 1: (40, 20) and (39, 19)
- Neutrons: 40 - 20 = 20 and 39 - 19 = 20 → Isotones
- Atomic Mass: 40 ≠ 39 → Not Isobars

2. Pair 2: (40, 20) and (40, 18)
- Neutrons: 40 - 20 = 20 and 40 - 18 = 22 → Not Isotones
- Atomic Mass: 40 = 40 → Isobars

3. Pair 3: (65, 29) and (65, 30)
- Neutrons: 65 - 29 = 36 and 65 - 30 = 35 → Not Isotones
- Atomic Mass: 65 = 65 → Isobars

4. Pair 4: (12, 6) and (16, 8)
- Neutrons: 12 - 6 = 6 and 16 - 8 = 8 → Not Isotones
- Atomic Mass: 12 ≠ 16 → Not Isobars

### Conclusion:
- From the analysis, we can conclude which pairs are isotones and which are isobars based on the calculations.