The necessary conditions for combustion process to occur are
1. availability of air/oxygen only
2. availability of air/oxygen and fuel
3. temperature of fuel below ignition temperature
4. temperature of fuel above ignition temperature
Select the correct alternative.

Options

A. 1 and 2
B. 2 and 4
C. 3 and 1
D. 4 and 1

Answer

To determine the necessary conditions for the combustion process to occur, we need to analyze each option provided in the question:

1. **Availability of air/oxygen only**:
- This option states that only air or oxygen is necessary for combustion. However, combustion requires both a fuel and oxygen to occur. Therefore, this option is incorrect.

2. **Availability of air/oxygen and fuel**:
- This option states that both air/oxygen and fuel are necessary for combustion. This is correct because combustion is a chemical process where a fuel reacts with oxygen to produce heat and light. Thus, this option is correct.

3. **Temperature of fuel below ignition temperature**:
- This option states that the temperature of the fuel must be below its ignition temperature. This is incorrect because ignition temperature is defined as the minimum temperature at which a substance starts to burn. If the temperature is below the ignition temperature, the fuel will not ignite.

4. **Temperature of fuel above ignition temperature**:
- This option states that the temperature of the fuel must be above its ignition temperature. This is correct because when the temperature of the fuel exceeds its ignition temperature, it will ignite and start the combustion process.

Based on the analysis above, the correct alternatives for the necessary conditions for combustion are:
- Option 2: Availability of air/oxygen and fuel (Correct)
- Option 4: Temperature of fuel above ignition temperature (Correct)

### Final Answer:
The correct alternatives are option 2 and option 4.