Why were many of the machines that sped up production and travel invented during the 18th and 19th centuries?
A. Rulers were finally funding scientific research.
B. There was finally a need for scientific discoveries.
C. Actually, most of them were produced during the 17th century.
D. There was a heightened interest in science during this time.
The reason why many of the machines that sped up production and travel invented during the 18th and 19th centuries is because "D. There was a heightened interest in science during this time," since this was during the age of the Enlightenment.
