Select all the correct answers.
In what three ways did the Chinese develop the perpetual calendar wan-nien-li?
A.) They observed the sun's longitude and the moon's phases.
B.) They used measurements from a sundial and a water clock.
C.) They determined the dates of the two solstices in a year.
D.) They mapped the constellations in the night sky.
E.) They surveyed citizens about how many days there should be in a year.
Choose 3 answers