Carbon dioxide is the primary greenhouse gas that is contributing to recent climate change, 72% of the totally emitted greenhouse gases is carbon dioxide (CO2), 18% Methane and 9% Nitrous oxide (NOx). Carbon dioxide emissions therefore are the most important cause of global warming.

Correct Option: D

Carbon dioxide is the primary greenhouse gas that is contributing to recent climate change, 72% of the totally emitted greenhouse gases is carbon dioxide (CO2), 18% Methane and 9% Nitrous oxide (NOx). Carbon dioxide emissions therefore are the most important cause of global warming.

A thin oil film on a water surface appears coloured because of thin-film interference which involves the interference of light waves reflecting off the top surface of a film with the waves reflecting from the bottom surface. The refractive index of oil is larger than that of water, therefore the reflection on the back side occurs.

Correct Option: B

A thin oil film on a water surface appears coloured because of thin-film interference which involves the interference of light waves reflecting off the top surface of a film with the waves reflecting from the bottom surface. The refractive index of oil is larger than that of water, therefore the reflection on the back side occurs.

A superconductor is a material that can conduct electricity or transport electrons from one atom to another with no resistance. No heat, sound or any other form of energy is released from the material when it reaches the temperature at which it becomes superconductive.

Correct Option: A

A superconductor is a material that can conduct electricity or transport electrons from one atom to another with no resistance. No heat, sound or any other form of energy is released from the material when it reaches the temperature at which it becomes superconductive.

The pin or needle floats because of an invisible elastic skin on the surface of the water. This elastic skin is called surface tension. Surface tension of the water leads to forces strong enough to support the needle’s weight.

Correct Option: A

The pin or needle floats because of an invisible elastic skin on the surface of the water. This elastic skin is called surface tension. Surface tension of the water leads to forces strong enough to support the needle’s weight.

Basic conditions to execute simple harmonic motion are: (i) There must be an elastic restoring force acting on the system, (ii) the system must have inertia, and (iii) the acceleration of the system should be directly proportional to its displacement and is always directed to mean position.

Correct Option: A

Basic conditions to execute simple harmonic motion are: (i) There must be an elastic restoring force acting on the system, (ii) the system must have inertia, and (iii) the acceleration of the system should be directly proportional to its displacement and is always directed to mean position.