Which of the following are classified as inner planets?

• A. Mercury, Venus, Earth, and Mars
• B. Jupiter, Saturn, Uranus, and Neptune
• C. Earth, Saturn, Venus, and Mars
• D. Mercury, Mars, Saturn, and Earth

Answer: (A)

The correct response identifies Mercury, Venus, Earth, and Mars as the inner planets of our solar system. These planets are characterized by their rocky compositions and are situated closer to the Sun than the gas giants. The inner planets are sometimes referred to as terrestrial planets because they have solid surfaces, unlike the outer planets, which are largely composed of gases and are located further from the Sun.

Mercury is the closest to the Sun and has no atmosphere, while Venus has a thick atmosphere that creates a strong greenhouse effect, making it the hottest planet. Earth is unique for its ability to support life, and Mars, known as the "Red Planet," has surface features similar to both Earth and the Moon, but it is smaller and has a thinner atmosphere.

In contrast, the other options include planets that do not fit the classification of inner planets, such as the gas giants Jupiter and Saturn and the ice giants Uranus and Neptune. These planets are found in the outer solar system and are much larger and predominantly made of hydrogen, helium, and other gaseous compounds, thus highlighting the distinction between inner and outer planets.