Consider the following statements: I. Without the atmosphere, temperature would be well below freezing point everywhere on the Earth's surface. II. Heat absorbed and trapped by the atmosphere maintains our planet's average temperature. III. Atmosphere's gases, like carbon dioxide, are particularly good at absorbing and trapping radiation. Which of the statements given above are correct?

I. Correct. Without the atmosphere and its greenhouse effect, Earth’s average surface temperature would be about -18°C, i.e. below freezing; the statement is broadly true in UPSC terms.
II. Correct. The atmosphere absorbs and re-emits outgoing terrestrial radiation, which helps maintain Earth’s average temperature.
III. Correct. Greenhouse gases such as carbon dioxide are effective at absorbing and trapping infrared radiation.

Hence, all three statements are correct.