What is the name of the earliest calculating machine which was based on concepts found in modern computers but was unfortunately never built?

Answer: Option A

Difference Engine, an early calculating machine, verging on being the first computer, designed and partially built during the 1820s and '30s by Charles Babbage. Charles Babbage began to construct a small difference engine in c. 1819 and had completed it by 1822 (Difference Engine 0).