The correct option is (a).
Explanation
Petroleum (crude oil) is a fossil fuel formed from the decomposition of ancient organic matter. This process, known as catagenesis, occurs over millions of years under specific geological conditions involving heat, pressure, and biological decay.
Statement-wise Analysis:
- Statement 1 is Correct: Petroleum was formed from organisms living in the sea (marine biomass like plankton and algae). As these organisms died, their bodies settled at the bottom of the sea and were gradually covered with layers of sand and clay.
- Statement 2 is Incorrect: The decomposition process required the absence of air (anaerobic conditions). The presence of air would have led to complete decay or oxidation, preventing the formation of hydrocarbons.
- Statement 3 is Incorrect: The transformation of dead organisms into petroleum and natural gas occurred under conditions of high temperature and high pressure deep beneath the Earth's surface, not low temperature and pressure.
Key Takeaway:
Petroleum formation requires the burial of marine organisms under anaerobic conditions (absence of air) subjected to high temperature and high pressure over geological time scales.