The process of converting ores into metal oxide in the absence of oxygen is calledA.RoastingB.CalcinationC.ReductionD.Leaching

The process of converting ores into metal oxide in the absence of oxygen is called Calcination. So, the answer is B. Calcination.

Here's a step-by-step explanation:

1. Roasting: This is a process where the ore is heated in the presence of excess air. It is done for sulfide ores. This process is not applicable here as it requires oxygen.

2. Calcination: This is a process where the ore is heated in the absence of air. This method is used to remove moisture, CO2, etc. from carbonate and hydrated ores. In this process, the ore is converted into metal oxide. So, this is the correct answer.

3. Reduction: This is a process where a substance loses oxygen or gains hydrogen. It is not applicable here as we are looking for a process that converts ores into metal oxide, not the other way around.

4. Leaching: This is a process where the ore is treated with a suitable reagent that dissolves the ore but not the impurities. This process is not applicable here as it does not involve converting ores into metal oxide.