Which two causes of decline were common to the Roman, Han, and Gupta empires?

answer; i believe that the correct answer is ; the eastern and western churches spoke different languages;

giant impact theory - the moon was formed from the collision between earth and another mars-sized body.

colliding planetesimals hypothesis - the moon was formed from the same cloud of material as earth.

capture hypothesis - the moon was locked into orbit by earths gravity as it was passing by it.

accretion hypothesis - the moon was formed from collisions and combining of planetesimals.

i think this is right, if not and you know better let me know.

i think it is the third one.