The greatest impact of the columbian exchange was
a) the annual storage of crops for native peoples.
b) the transport of slaves from the americas to africa.
c) the spread of new diseases, which led to vaccinations.
d) the transfer of plants, people, and ideas between the americas, europe, and africa.

The telegraph, the transatlantic telegraph cable, and the telephone were important to businesses after 1850 because of a. they created a system for developing new inventions. b. they filled a need that other inventions of the day could not. c. they attracted investors and created the stock market. d. they made picture-taking a popular american pastime.