During the columbian exchange, natives of the americas were introduced to

potatoes.

corn.

cattle.

beavers.

The correct answer is: Cattle

With the Columbian exchange Europeans introduced some things to America and took some others that were unknown to them.

Potato and corn were well known foods to the Americans, the Aztec's main food was corn and the Inca's one potato.  

One of the main species of beaver has it's origin in America, the Castor Canadensis whose ancestor migrated from Asia about 7.5 million years ago.

Therefore, cattle is correct. When the spanish people arrived America they brought horses and pigs in their secound journey, unknown for the natives. As an example, the Aztecs often believed that a Spanish riding a horse was a two headed creature. Later on cows were also introduced.

by 1880, germany had more rail lines than great britain and russia.

agriculture revolution