Based on current consumption rates, the known reserves of fossil fuels are expected to last for:

Correct Option

The correct option is

A limited period of a few hundred years

Explanation

Fossil fuels (coal, petroleum, and natural gas) are non-renewable organic resources formed from the decomposition of carbon-based organisms over millions of years. Due to the specific geological conditions required for their formation, they exist in finite quantities in the Earth's crust.

Analysis of Options:

• An unlimited period is incorrect: Fossil fuels are exhaustible resources. Since they are not being replenished at a scale relevant to human usage, they cannot last for an unlimited period.
• Millions of years is incorrect: While the formation of fossil fuels takes millions of years, the depletion of known reserves is occurring rapidly. They will not last for millions of years under current usage patterns.
• A limited period of a few hundred years is correct: At current consumption rates, proven reserves of crude oil and natural gas are estimated to last for several decades (approximately 50 years), while coal reserves are expected to last for roughly 100 to 200 years. Consequently, the total availability of these fuels is limited to a few hundred years.
• A renewable cycle of one year is incorrect: Fossil fuels are non-renewable and do not regenerate within a human timeframe or an annual cycle.

Key Takeaway: Fossil fuels are finite, non-renewable organic compounds, and their known reserves are projected to be exhausted within a few centuries due to high rates of consumption.