Explanation:

Introduction:
The statement mentions that an ice cube was observed to have melted due to the heat of a nearby furnace. We are asked to determine whether this situation, where an ice cube melts due to the heat of a nearby furnace, always, never, often, or sometimes occurs.

Understanding the situation:
To answer this question, we need to consider the properties of ice and the effects of heat. Ice is the solid state of water, and it melts at temperatures above 0 degrees Celsius (32 degrees Fahrenheit). Heat, on the other hand, is a form of energy that can increase the temperature of objects.

Effect of heat on ice:
When heat is applied to ice, it transfers energy to the ice molecules, causing them to vibrate faster. As a result, the temperature of the ice increases, and if it reaches the melting point (0 degrees Celsius or 32 degrees Fahrenheit), the ice will start to melt and transform into liquid water.

Impact of a nearby furnace:
A furnace is a heating system that generates high temperatures. If an ice cube is exposed to the heat emitted by a nearby furnace, it is likely that the temperature of the ice cube will rise. If the temperature of the ice cube surpasses its melting point (0 degrees Celsius or 32 degrees Fahrenheit), the ice will melt and turn into liquid water.

Conclusion:
Based on the understanding of how heat affects ice and the presence of a nearby furnace, it can be concluded that the ice cube will always melt due to the heat of a nearby furnace. Therefore, the correct answer is option 'A' (Always).