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