Big bang theory explains
(a) Origin of earth
(b) Origin of universe
(c) Origin of ocean
(d) Origin of first life

Options

A. Origin of earth
B. Origin of universe
C. Origin of ocean
D. Origin of first life

Answer

To solve the question "Big Bang theory explains," we need to analyze each of the options provided:

1. **Understanding the Big Bang Theory**: The Big Bang Theory is a scientific explanation for the origin of the universe. It posits that the universe began as a singular point approximately 13.7 billion years ago and has been expanding ever since.

2. **Evaluating the Options**:
- **(a) Origin of Earth**: The Big Bang Theory does not specifically explain the formation of Earth. Earth formed later, about 4.5 billion years ago, from the remnants of the solar nebula.
- **(b) Origin of Universe**: This option aligns with the Big Bang Theory, which describes how the universe began and has been expanding.
- **(c) Origin of Ocean**: The formation of oceans is a separate process that occurred after the Earth was formed, primarily through volcanic outgassing and the accumulation of water from comets and asteroids.
- **(d) Origin of First Life**: The Big Bang Theory does not address the origin of life. The origins of life are studied in fields like abiogenesis and evolutionary biology.

3. **Conclusion**: Based on the analysis, the correct answer is (b) Origin of Universe, as the Big Bang Theory specifically explains how the universe originated and continues to expand.

### Final Answer:
(b) Origin of universe