Undesirable Changes:
Undesirable changes refer to those changes that are not useful to us and may cause harm. These changes are generally unwanted and can have negative consequences. Let's look at the examples to understand this concept better.

Examples of Undesirable Changes:
The correct answer option is 'D', which means both eruption of volcano and rusting of iron are examples of undesirable changes. Let's discuss each example in detail:

1) Eruption of volcano:
When a volcano erupts, it releases a mixture of hot lava, ash, and gases into the atmosphere. This can have devastating effects on the surrounding environment and human settlements. Volcanic eruptions can cause destruction of land, loss of life, and damage to infrastructure. Therefore, it is considered an undesirable change.

2) Rusting of iron:
Rusting is a chemical process that occurs when iron comes into contact with moisture and oxygen in the air. It leads to the formation of rust, which is a reddish-brown flaky substance. Rusting weakens the iron and causes it to deteriorate over time. This can be harmful, especially when it affects important structures like bridges, vehicles, or machinery. Rusting is an undesirable change because it reduces the strength and durability of iron.

3) Melting of ice:
The melting of ice is not considered an undesirable change. It is a natural process that occurs when ice is exposed to higher temperatures. Melting ice is essential for the water cycle and is necessary for the survival of many organisms. It helps in replenishing water sources such as rivers, lakes, and groundwater. Therefore, the melting of ice is not an undesirable change.

To summarize, undesirable changes are those changes that are not useful to us and may cause harm. Examples of undesirable changes include the eruption of volcanoes and rusting of iron. These changes have negative consequences and can lead to destruction, loss, or deterioration. However, the melting of ice is not an undesirable change as it plays a vital role in maintaining the water cycle.

Melting of ice can be desirable because this change is not harmful and we also use ice in our day to day life but option d is totally the change that we don't want it in any part of our life and they are harmful for us.