Holme's signals produce burning gases which serve as a signal to the approaching ships contains.

Options

A. A mixture of `Ca_3 P_2` and `CaC_2`
B. A mixture of `Ca_3 P_2` and `KOH`
C. A mixture of `CaC_2` and `KOH`
D. A mixture of `CaP_2, CaC_2` and `KOH`.

Answer

To solve the question about Holme's signals and the burning gases they produce, we need to analyze the given options and their reactions. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Components
Holme's signals involve the use of certain chemical mixtures that produce burning gases. The options provided are:
1. Mixture of Ca3P2 and CaCO2
2. Mixture of Ca3P2 and KOH
3. Mixture of CaCO2 and KOH

### Step 2: Analyze Each Option
We will analyze the reactions of each mixture to determine which one produces burning gases.

#### Option 1: Mixture of Ca3P2 and CaCO2
- When calcium phosphide (Ca3P2) reacts with water, it produces calcium hydroxide (Ca(OH)2) and phosphine (PH3), which is a flammable gas.
- The reaction can be represented as:
\[ Ca3P2 + 6H2O \rightarrow 3Ca(OH)2 + 2PH3 \]
- The phosphine (PH3) can ignite and produce flames.

#### Option 2: Mixture of Ca3P2 and KOH
- Calcium phosphide (Ca3P2) reacting with potassium hydroxide (KOH) does not produce a significant amount of burning gas compared to the first option.

#### Option 3: Mixture of CaCO2 and KOH
- Calcium carbide (CaC2) reacts with water to produce acetylene (C2H2), which is a flammable gas.
- The reaction can be represented as:
\[ CaC2 + 2H2O \rightarrow C2H2 + Ca(OH)2 \]
- The acetylene (C2H2) can ignite and produce flames.

### Step 3: Determine the Correct Answer
From the analysis:
- Option 1 produces phosphine (PH3), which ignites and burns.
- Option 3 produces acetylene (C2H2), which also ignites and burns.

However, the question specifically mentions Holme's signals, which are traditionally associated with the burning of phosphine. Therefore, the correct answer is:

**Correct Answer: Mixture of Ca3P2 and CaCO2 (Option 1)**

### Summary
Holme's signals produce burning gases through the reaction of calcium phosphide with water, generating phosphine, which ignites and serves as a signal.