The correct answer is 29 days. To find the answer to this question, you can consult a reliable source such as an astronomy textbook or do a quick search online. The moon goes through a complete cycle of its phases, known as the lunar month, in approximately 29.5 days. This period is also referred to as a synodic month. It is important to note that this time frame can vary slightly due to the moon's elliptical orbit around the Earth.