For welding mixture Ethine and . . . . . . . . is used.

The correct answer is Option B: oxygen.

Let's understand why:

1. Ethine is also commonly known as Acetylene (C2H2). It is a gas that burns very easily and releases a lot of heat.
2. For welding, we need an extremely hot flame to melt and join metals. To make Ethine (Acetylene) burn with such high intensity, it needs to be mixed with pure oxygen.
3. This process is called Oxy-acetylene welding. When Ethine burns in pure oxygen, it produces a flame that can reach temperatures over 3000°C! This incredible heat is what makes it suitable for cutting and welding metals.
4. Using pure oxygen provides a much hotter and more concentrated flame compared to burning Ethine in just air, because air only contains about 21% oxygen (the rest is mostly nitrogen, which doesn't help with burning).

Let's see why the other options are not correct:

* Option A: ethanol is an alcohol. While it burns, it does not produce the extremely high temperatures required for industrial welding of metals.
* Option C: carbon dioxide is a gas that is often used to put out fires (like in fire extinguishers), not to make them burn hotter or support combustion.
* Option D: air contains oxygen, but also a lot of nitrogen and other gases. Burning Ethine with air would create a flame, but it wouldn't be nearly as hot or efficient for welding as a flame created with pure oxygen.