Which statements explain why independent city-states emerged in ancient greece?

choose all answers that are correct.

a.

trade between the different city-states enhanced communication.

b.

rivers provided a means of navigable travel and communication.

c.

some city-states were located on isolated islands.

d.

the seas were sometimes difficult to navigate and limited communication.

One thing was that Seas were sometimes difficult to navigate which limited communication - D. this was already a factor which limited the possibility of one united Greece emergin because it made it very difficult to talk to these isolated islands that couldbe found through the difficult-to-navigate seas.

Another thing was that C - some city-states were located on isolated islands. 

There all correct when humanity revitos lifes own lies it's disgusting