Venus is the planet that is nearest to the Earth. Venus is often referred to as the “sister planet” of the Earth. This is due to the fact that Venus is of similar size and composition to the Earth. Moreover, Venus is situated right next to the Earth. Given the options of Neptune, Mars, Venus, and Mercury, the correct answer is Venus. Neptune is too far off, Mars is farther off from the Earth than Venus is, and Mercury is the planet that is nearest to the Sun. Thus, the correct answer is (C) Venus.