Of the following statements:
(a) `C_(6)H_(5)N=CH-C_(6)H_(5)` is a Schiff's base
(b) A dye is obtained by the reaction of aniline and `C_(6)H_(5)N=NCl`
(c) `C_(6)H_(5)CH_(2)NH_(2)` on treatment with `[NaNO_(2) + HCl]` gives diazonium salt
(d) p-Toluidine in treatment with `[HNO_(2) + HCl]` gives diazonium salt

Options

A. Only (a) and (b) are correct
B. Only (a) and (c) are correct
C. Only (c) and (d) are correct
D. (a),(b) and (d) are correct

Answer

To solve the question regarding the statements about amines and their reactions, we will analyze each statement step by step.

### Step-by-Step Solution:

**Statement (a):** `C_(6)H_(5)N=CH-C_(6)H_(5)` is a Schiff's base.

1. **Definition of Schiff's Base:** A Schiff's base is an imine formed by the condensation of an amine with an aldehyde or ketone. It has the general structure R2C=NR'.
2. **Analysis of the Given Compound:** The compound `C_(6)H_(5)N=CH-C_(6)H_(5)` can be rewritten as `Ph-N=CH-Ph`, where Ph represents the phenyl group (C6H5).
3. **Conclusion:** Since it has the structure of an imine, it is indeed a Schiff's base.

**Result:** Statement (a) is **correct**.

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**Statement (b):** A dye is obtained by the reaction of aniline and `C_(6)H_(5)N=NCl`.

1. **Understanding the Reaction:** Aniline (C6H5NH2) can react with benzene diazonium chloride (C6H5N2Cl) in a coupling reaction.
2. **Mechanism:** In this reaction, the diazonium salt acts as an electrophile and substitutes at the para position of aniline, forming an azo dye.
3. **Conclusion:** The product of this reaction is indeed a dye, specifically an azo dye.

**Result:** Statement (b) is **correct**.

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**Statement (c):** `C_(6)H_(5)CH_(2)NH_(2)` on treatment with `[NaNO_(2) + HCl]` gives diazonium salt.

1. **Analyzing the Compound:** The compound `C_(6)H_(5)CH_(2)NH_(2)` is benzylamine.
2. **Reaction with NaNO2 and HCl:** When benzylamine is treated with sodium nitrite (NaNO2) and hydrochloric acid (HCl), it forms an unstable diazonium salt (C6H5CH2N2Cl).
3. **Stability of the Diazonium Salt:** Benzyl diazonium chloride is unstable and decomposes to form benzyl alcohol and nitrogen gas upon warming.
4. **Conclusion:** Therefore, while a diazonium salt is formed, it is not stable.

**Result:** Statement (c) is **incorrect**.

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**Statement (d):** p-Toluidine in treatment with `[HNO_(2) + HCl]` gives diazonium salt.

1. **Understanding p-Toluidine:** p-Toluidine (C6H4(CH3)NH2) is an aromatic amine.
2. **Reaction with HNO2 and HCl:** When p-toluidine is treated with nitrous acid (generated from NaNO2 and HCl), it forms the corresponding diazonium salt (p-toluidine diazonium chloride).
3. **Conclusion:** This reaction is valid and leads to the formation of a stable diazonium salt.

**Result:** Statement (d) is **correct**.

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### Final Conclusion:
- Statements (a), (b), and (d) are correct.
- Statement (c) is incorrect.

Thus, the correct answer is that statements A, B, and D are correct.