The correct answer is: B. increase in yield per hectare.
Wheat production has increased significantly in recent years, due in large part to increases in yield per hectare. This is due to a number of factors, including improved crop varieties, better irrigation practices, and the use of fertilizers and pesticides.
Increased area under wheat cultivation has also contributed to the increase in production, but to a lesser extent. This is because the amount of land that is suitable for wheat cultivation is limited, and there are other crops that can be grown on this land that are more profitable.
Increased demand for wheat has not been a major factor in the increase in production, as the global demand for wheat has been relatively stable in recent years. However, if demand were to increase significantly, this could lead to further increases in production.
Increase in prices has not been a major factor in the increase in production, as the prices of wheat have been relatively stable in recent years. However, if prices were to increase significantly, this could lead to further increases in production.