`NH_(4)SCN` can be used to test one or more out of `Fe^(3+) , Co^(2+) , Cu^(2+)`:

Options

A. `Fe^(3+)` only
B. `Co^(2+), Cu^(2+)` only
C. `Fe^(3+), Cu^(2+)` only
D. All

Explanation

To determine which ions can be tested using ammonium thiocyanate (NH₄SCN), we will analyze the reactions of NH₄SCN with each of the ions: Fe³⁺, Co²⁺, and Cu²⁺.

### Step-by-Step Solution:

1. **Identify the Ions**: The ions we need to test are Fe³⁺ (Iron), Co²⁺ (Cobalt), and Cu²⁺ (Copper).

2. **Reactions with NH₄SCN**:
- **For Fe³⁺**:
- When Fe³⁺ reacts with NH₄SCN, it forms a deep red precipitate of iron(III) thiocyanate complex, denoted as [Fe(SCN)]²⁺.
- Reaction:
\[ \text{Fe}^{3+} + \text{NH}_4\text{SCN} \rightarrow [\text{Fe(SCN)}]^{2+} \text{ (deep red precipitate)} \]
- Conclusion: Fe³⁺ can be detected using NH₄SCN.

- **For Co²⁺**:
- When Co²⁺ reacts with NH₄SCN, it forms a blue precipitate of cobalt(II) thiocyanate complex, denoted as [Co(SCN)]²⁺.
- Reaction:
\[ \text{Co}^{2+} + \text{NH}_4\text{SCN} \rightarrow [\text{Co(SCN)}]^{2+} \text{ (blue precipitate)} \]
- Conclusion: Co²⁺ can also be detected using NH₄SCN.

- **For Cu²⁺**:
- When Cu²⁺ reacts with NH₄SCN, it forms a black precipitate of copper(I) thiocyanate, denoted as Cu₂(SCN)₂.
- Reaction:
\[ \text{Cu}^{2+} + 2\text{NH}_4\text{SCN} \rightarrow \text{Cu}_2(\text{SCN})_2 \text{ (black precipitate)} \]
- Conclusion: Cu²⁺ can also be detected using NH₄SCN.

3. **Final Conclusion**:
- All three ions (Fe³⁺, Co²⁺, and Cu²⁺) can be detected using NH₄SCN, as each forms a distinct colored precipitate.

### Summary:
- **Fe³⁺**: Deep red precipitate
- **Co²⁺**: Blue precipitate
- **Cu²⁺**: Black precipitate

Thus, the answer is that NH₄SCN can be used to test for all three ions: Fe³⁺, Co²⁺, and Cu²⁺.