Answer:  Option A - The speed of light is constant in all frames of reference.

Explanation:

• Einstein's theory of relativity fundamentally states that the speed of light in a vacuum is constant and independent of the observer's motion.
• This principle underpins the idea that space and time are interwoven into a single fabric called spacetime, where gravity curves spacetime.
• The other options are incorrect as they misrepresent the theory’s predictions about gravity, time dilation, and mass-energy equivalence.

Answer:  Option A - Light echoes occur when light from distant stars bends due to a black hole's gravity and reaches Earth at different times.

Explanation:

• Light echoes occur when light from a distant object, such as a star, passes near a black hole and gets bent by its strong gravitational field.
• As a result, the light reaches Earth at different times, creating an "echo" effect.
• This phenomenon enables scientists to measure the black hole's mass and spin by analyzing the time delay between the original light and its echoed counterpart, offering insights into the black hole's properties.

Answer:  Option B - A system for trading carbon emissions allowances to incentivize emission reductions.

Explanation:

• A carbon market is a system that facilitates the trading of carbon emission allowances, where entities like companies or governments can buy and sell rights to emit a certain amount of greenhouse gases.
• The goal is to cap overall emissions and provide an economic incentive for reducing emissions.
• By allowing flexible trading, it encourages the adoption of cleaner technologies and emission reduction strategies, helping to address climate change.

Answer:  Option A - Their unique nesting behaviour where thousands of females come ashore simultaneously to lay eggs.

Explanation:

• "Arribadas" is a term used to describe the mass nesting behavior of Olive Ridley turtles, where thousands of female turtles come ashore simultaneously to lay their eggs.
• This phenomenon occurs at specific beaches during the breeding season, and it is one of the most remarkable behaviors in the animal kingdom.
• During an arribada, the turtles nest in large numbers, ensuring the survival of their species through synchronized reproduction.