Which statement about the Moon cycle is correct?

• A. It lasts 12 hours
• B. It lasts 29.5 days and begins with waxing.
• C. It lasts 100 days
• D. It lasts 365 days

Answer: (B)

Think about how the Moon’s appearance changes in a regular pattern each month. The key idea being tested is how long that cycle lasts. The Moon goes through a sequence of phases as sunlight hits different parts of it from Earth’s perspective, and this sequence repeats roughly every 29.5 days. That length—the time from one new-moon phase back to the next new-moon phase—is the cycle’s duration.

After a new moon, you start to see light grow on the near side—the Moon waxes—so the illuminated portion increases through crescent, first quarter, and waxing gibbous until it reaches a full moon. Then the light wanes as it moves back toward a new moon, completing the cycle. So the statement that the Moon cycle lasts about 29.5 days captures the correct timespan, and it reflects the waxing portion that occurs early in the cycle. The other choices describe durations that don’t match what we observe for this monthly cycle: about half a day is far too short, around 100 days is too long, and a year is the time it takes Earth to orbit the Sun.