Which pair of events shows a cause-and-effect relationship!

a. egyptians develop the square-rigged ship.
large-scale irrigation projects begin.
b. hyksos invade the nile delta region.
horse-drawn chariots come into use.
c. queen hatshepsut becomes pharaoh.
amenhotep iv takes the throne.
d. last native pharaoh rules.
persia again conquers egypt.