Which development helped make the cattle business on the Great Plains profitable?

ANative Americans developed a taste for beef and bought entire herds.
BWorkmen on the transcontinental railroad used cattle to pull heavy wagon loads.
CBarbed wire fencing made it easier to drive cattle herds long distances.
DGrowing populations in eastern cities greatly increased the demand for beef.

Verified Answer :

It was primarily that "D. Growing populations in eastern cities greatly increased the demand for beef," since along with the advent of the rail lines, getting the meat to the consumer was far easier. 

Answer:

D. Growing populations in eastern cities greatly increased the demand for beef.

Explanation: