The Big Bang theory explains the origin of which of the following?

The correct answer is C, Universe. The Big Bang theory is a cosmological model describing how the universe began as a hot, extremely dense state and has been expanding ever since. Its main support comes from Hubble's observation of galactic redshift (1929), the cosmic microwave background discovered in 1964, and the observed abundance of light elements. The current estimate of the age of the universe is about 13.8 billion years.

• Mammals: Wrong. Their origin is explained by biological evolution through natural selection, not cosmology. Early mammals appeared in the Mesozoic era, roughly 200 million years ago.
• Ice Age: Wrong. Glacial periods are explained by changes in Earth's orbit and axial tilt (Milankovitch cycles), atmospheric composition and ocean circulation.
• Ocean: Wrong. Earth's oceans formed as water vapour from volcanic outgassing condensed while the planet cooled, billions of years after the universe itself formed.

The concept links to the GS-III syllabus under space and science, and it is useful in Mains for questions on scientific temper and how evidence shapes theory.

Trap: Aspirants often confuse the origin of the universe with the origin of life or of Earth. The Big Bang explains only the universe.