Cyrus mccormick's 1834 invention was used for

Cyrus McCormick in 1831. This machine was used by farmers to harvest crops mechanically. For hundreds of years, farmers and field workers had to harvest crops by hand using a sickle or other methods, which was an arduous task at best

Cyrus McCormick's 1834 invention was used to harvest crops mechanically.

(d) it was complex and capable of highly organized efforts.

Ithink a is the answer