A teacher challenges students to study moon phases to determine if what they have learned from the textbook is accurate. How might a student investigate claims made in a textbook that moon phases occur in a 28-day cycle?

a.observe the phase of the moon each night until a full moon can be seen.
b.compare the textbook phases to the actual moon phases seen in the night sky each night in 28 day period over a three-month time frame.
c.compare diagrams of moon phases from the textbook to diagrams of moon phases online
d.observe the moon phases are seen in the night sky as often as possible over a six month period