The melting point of a substance is the temperature at which it changes from a solid to a liquid state. In the case of iron, the correct melting point is option 4, which is 1500°C. This means that at temperatures below 1500°C, iron exists as a solid, and at temperatures above 1500°C, it melts and becomes a liquid.

Option 1, which is 25°C, is incorrect because this is a very low temperature, and iron does not melt at such low temperatures. Iron has a high melting point, so it requires significantly higher temperatures for it to change from a solid to a liquid.

Option 2, which is 37°C, is also incorrect for the same reason. This temperature is still too low for iron to melt. Iron is commonly known for its strength and durability, and this is due in part to its high melting point.

Option 3, which is 500°C, is closer to the correct answer compared to the previous options. However, it is still too low for iron to melt. Iron requires much higher temperatures to reach its melting point.

Therefore, the correct answer is option 4, 1500°C, as this is a temperature at which iron can melt and transition from a solid