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.

1.d 2.a c.!

the causes of the dust bowls were severe droughts,   lands became dry and hard, temperature was higher than usual, hot and dry conditions killed crops, high winds. because of those factors, the winds kicked up dry soil and created clouds of dust.