Final answer:
Mars, known for its distinctive red color, is referred to as the Red planet and is the correct answer to the question (b).
Step-by-step explanation:
The planet that is commonly referred to as the Red planet is Mars (b). Mars is known for its distinctive red color, which is visible from Earth. This characteristic hue is due to the iron oxide, commonly known as rust, on its surface. Despite Mars sometimes being nearly as bright as Venus when close to Earth, typically it is less conspicuous in the night sky. The ancients were aware of the Red planet, and its exploration has been a significant focus in recent decades due to evidence suggesting that it may have had conditions suitable for life in the past. Today, Mars captivates the interest of scientists and the public alike as it is considered one of the most likely places for future human habitat.