What physical feature had the greatest effect on China's contact with other countries? O Vast, flat deserts made northward travel easier.
O Extensive highlands made westward travel difficult.
O River systems helped travel between north and south.
O High, dangerous mountains blocked southward travel.

A. vast, flat deserts made northward travel easier.

Explanation:

i got it from another question just like this one so if its wrong i'm sorry. they just keep saying in the comments that it was A . so if i'm wrong i'm sorry

a social contract.

"a social contract is an agreement between citizens and their leader where the citizens give up certain freedoms in exchange for protection. the constitution of the united states is an example of a social contract."

while it was true that the cotton gin reduced the labor of removing seeds, it did not reduce the need for slaves to grow and pick the cotton.

explanation:

before eli whitney's invention of the cotton gin, picking and cleaning cotton was a slow, labor-intensive job. workers, usually slaves, had to pick the seeds from the cotton fibers by hand. this invention made it possible to grow large amounts of cotton on big farms and make money.