Answer the following question: Fact 1: Aplanet rotating causes cycles of day and night on that planet. Fact 2: Rotation simply means how long it takes a planet to spin on its axis. Given the two facts above, what causes day and night cycles on a planet?

Pick from:
[1]. seasons.
[2]. carbon dioxide.
[3]. flow of electrons.
[4]. gravitational pull.
[5]. fissures of hot, acidic water.
[6]. spinning on its axis.
[7]. heat energy.
[8]. energy of moving objects.
Answer:
[6].