The correct answer is: Hunting and gathering.

Explanation:

The Mesolithic period (Middle Stone Age) is characterized by a transitional phase between the Paleolithic (Old Stone Age) and Neolithic (New Stone Age). During this period, human societies primarily relied on hunting, gathering, and fishing as their main economic activities. However, they also began experimenting with early forms of domestication and primitive agriculture.

Key Features of the Mesolithic Economy:

1. Hunting and Gathering:
   • The primary source of food was hunting animals and gathering wild plants, nuts, and fruits.
   • Tools like microliths (small, sharp stone tools) were used to make weapons like arrows and harpoons for more efficient hunting.
2. Fishing:
   • Fishing became an important activity, with the development of tools like fish hooks and nets.
3. Early Domestication:
   • While the Mesolithic economy was predominantly based on hunting and gathering, some evidence suggests the beginning of animal domestication (e.g., dogs) and rudimentary agriculture.
4. Seasonal Settlements:
   • People began living in semi-permanent shelters as they exploited resources in specific areas.

Why Other Options Are Incorrect:

1. Agriculture:
   • Agriculture became the dominant economic activity in the Neolithic period, not the Mesolithic period.
2. Pastoralism:
   • While early domestication began in the Mesolithic period, full-fledged pastoralism emerged later during the Neolithic period.
3. Industry:
   • The concept of industry is associated with much later periods, such as the Industrial Revolution.

Thus, the economy of the Mesolithic period was primarily based on hunting and gathering.

The correct answer is Stone tools.

Explanation:

The Paleolithic period (Old Stone Age) is characterized by the use of stone tools, as this was a time before humans discovered how to work with metals. Early humans made tools primarily from stone, and these tools were used for hunting, gathering, and basic survival tasks.

Why other options are incorrect:

1. Iron tools: Iron tools were developed much later, during the Iron Age (around 1200 BCE onwards).
2. Bronze tools: Bronze tools belong to the Bronze Age (around 3300–1200 BCE), which followed the Neolithic period.
3. Copper tools: Copper tools were first used in the Chalcolithic period (Copper Age), which came after the Stone Age.

The Paleolithic period is defined by the use of stone tools only.

The main principles of thermodynamics are encapsulated in the four laws of thermodynamics, which provide a framework for understanding energy, heat, and work in physical systems. These laws are foundational in physics, chemistry, and engineering. Here’s an overview:

Zeroth Law of Thermodynamics

• Statement: If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
• Significance: It defines the concept of temperature and forms the basis for temperature measurement.

First Law of Thermodynamics (Law of Energy Conservation)

• Statement: Energy cannot be created or destroyed; it can only be transferred or transformed. Mathematically:

                                                                            ΔU=Q−W Where:

• • ΔU: Change in internal energy of the system
  • Q: Heat added to the system
  • W: Work done by the system

• Significance: It establishes the principle of energy conservation and explains how energy transitions between heat and work in a system.

Second Law of Thermodynamics

• Statement: The entropy of an isolated system always increases or remains constant over time; it never decreases. For practical processes, entropy tends to increase.
• Significance:
  • Introduces the concept of irreversibility in natural processes.
  • Provides the direction of energy flow (e.g., heat flows from a hot body to a cold one).
  • Forms the basis for the concept of efficiency in engines and refrigerators.

Third Law of Thermodynamics

• Statement: As the temperature of a system approaches absolute zero (0 Kelvin), the entropy of the system approaches a constant minimum value.
• Significance: It implies that absolute zero is unattainable and provides insight into the behavior of systems at very low temperatures.

These principles collectively govern how energy and matter interact and transform in all physical processes.

The “Satellite Man of India” is Professor Udupi Ramachandra Rao. He was a prominent Indian space scientist and the chairman of the Indian Space Research Organisation (ISRO). Prof. Rao is best known for overseeing the launch of Aryabhata, India’s first satellite, in 1975. His contributions to India’s space program were significant, particularly during his tenure from 1984 to 1994, which saw remarkable advancements in satellite technology and applications.Prof. Rao was instrumental in establishing satellite technology in India and led various projects that enhanced communication, remote sensing, and meteorological services. He was honored with several awards, including the Padma Vibhushan and induction into the Satellite Hall of Fame, recognizing his pivotal role in shaping India’s space capabilities.