**Answer:**

The correct answer is option D) Chalcolithic.

**Explanation:**

Copper, one of the first metals ever utilized by humans, was discovered during the Chalcolithic period. The Chalcolithic age, also known as the Copper Age, was a transitional period between the Neolithic (New Stone Age) and the Bronze Age. It was characterized by the use of copper tools and weapons alongside stone tools.

Here is a detailed explanation of the Chalcolithic period and its significance in the discovery of copper:

1. **Chalcolithic Period:** The Chalcolithic period, also known as the Eneolithic or the Copper Age, occurred between the Neolithic and Bronze Age periods, approximately around 4500 BCE to 3500 BCE. It was a time of significant technological advancements and cultural changes.

2. **Copper Discovery:** During the Chalcolithic period, humans discovered the use of copper. They realized that copper could be extracted from ores and shaped into tools and weapons. This discovery revolutionized human civilization, as it allowed for the development of more efficient tools and the advancement of metallurgy.

3. **Copper Tools and Weapons:** The discovery of copper led to the production of a wide range of tools and weapons. Copper tools were more durable and efficient compared to stone tools. They included axes, knives, chisels, and awls. Copper was also used to make weapons such as daggers and spearheads.

4. **Advantages of Copper:** Copper tools and weapons provided several advantages over stone tools. Copper is a softer metal, making it easier to shape and sharpen. It also has better resistance to wear and tear, making it more durable. Copper tools were also more effective in farming, construction, and warfare.

5. **Impact on Civilization:** The discovery of copper and the use of copper tools had a profound impact on human civilization. It marked the transition from the Stone Age to the Bronze Age, where the use of metal became more prevalent. It laid the foundation for the development of metallurgy and the subsequent advancements in technology.

In conclusion, copper was discovered during the Chalcolithic period, which was a transitional phase between the Neolithic and Bronze Age. The discovery of copper revolutionized human civilization, leading to the production of more efficient tools and weapons and laying the foundation for the development of metallurgy.

**Explanation:**

The correct answer is option 'D' - Chalcolithic.

**Chalcolithic Age:**
The Chalcolithic Age, also known as the Copper Age, is a period in human history that falls between the Neolithic Age and the Bronze Age. It is characterized by the use of copper tools and ornaments, along with stone tools. The Chalcolithic Age is estimated to have occurred around 4500 to 3500 BCE.

**Discovery of Copper:**
Copper, a reddish-brown metal, was one of the first metals to be discovered and used by humans. It played a significant role in the development of early civilizations. The discovery of copper marked a significant technological advancement as it allowed humans to create tools and weapons that were more durable and efficient than those made solely from stone.

**Copper and the Chalcolithic Age:**
During the Chalcolithic Age, humans began to experiment with mining and smelting techniques to extract and work with copper. The word "Chalcolithic" itself is derived from the Greek words "khalkos" meaning copper and "lithos" meaning stone.

**Advantages of Copper:**
The discovery of copper had several advantages for early humans. Some of them are:

1. **Improved Tools and Weapons:** Copper allowed for the creation of tools and weapons that were stronger and more durable than those made from stone. Copper tools, such as axes and knives, were sharper and more efficient in cutting and shaping materials.

2. **Ornaments and Jewelry:** Copper was also used to create decorative objects, such as jewelry and ornaments. These objects served as symbols of status and wealth within early societies.

3. **Trade and Exchange:** The availability of copper allowed for increased trade and exchange between different regions. Copper became a valuable commodity that was exchanged for other goods and resources.

4. **Technological Advancements:** The discovery and use of copper marked a significant step forward in human technological advancements. It paved the way for the development of metallurgy and the eventual transition to the Bronze Age, where copper was alloyed with tin to create bronze.

In conclusion, copper was discovered and utilized by humans during the Chalcolithic Age, also known as the Copper Age. The discovery of copper had numerous advantages and played a crucial role in the development of early civilizations.