The gas used in the welding and cutting of metal is:A.EthaneB.EtheneC.EthyneD.Propene

The gas used in welding and cutting of metal is **C. Ethyne** (commonly known as acetylene).

### Explanation:

1. **Ethyne (Acetylene)**:
- Ethyne is a hydrocarbon with the formula \(C_2H_2\).
- It is widely used in welding and cutting metals due to its high flame temperature when burned in oxygen, which can reach about 3,500 °C (6,332 °F).
- The high temperature allows it to easily melt and cut through metal.

2. **Other Options**:
- **A. Ethane (\(C_2H_6\))**: A saturated hydrocarbon (alkane) that is primarily used as a fuel but does not have the same high-temperature combustion properties as ethyne.
- **B. Ethene (\(C_2H_4\))**: An unsaturated hydrocarbon (alkene) used mainly as a precursor for plastics and other chemicals, not suitable for welding or cutting.
- **D. Propene (\(C_3H_6\))**: Another unsaturated hydrocarbon (alkene) primarily used in the production of plastics and chemicals. It can be used as a fuel but is less effective than ethyne for welding.

### Conclusion:
Ethyne is the preferred gas for welding and cutting metals due to its ability to produce a very high-temperature flame, making option **C** the correct answer.