Pick up the correct statement from the following: A. Roasting is not necessary if iron ore is an oxide B. Impurities float on the molten iron as slag C. The slag contains lime about 45% D. All the above

The correct answer is D. All the above.

Roasting is not necessary if iron ore is an oxide because the ore can be directly reduced to iron. However, roasting is often done to improve the quality of the ore by removing impurities. Impurities float on the molten iron as slag, which is then removed. The slag contains lime about 45%.

Here is a more detailed explanation of each option:

• Roasting is not necessary if iron ore is an oxide. This is because the ore can be directly reduced to iron without roasting. However, roasting is often done to improve the quality of the ore by removing impurities.
• Impurities float on the molten iron as slag. This is because the impurities are less dense than the molten iron. The slag is then removed from the molten iron.
• The slag contains lime about 45%. This is because lime is a common impurity in iron ore. The lime is removed from the molten iron as slag.

I hope this explanation is helpful. Please let me know if you have any other questions.