Correct Answer: 1848

Solution : The correct answer is 1848.

Louis Pasteur's seminal work in this area began in the early 1840s and culminated in his famous discovery in 1848. In 1848, Pasteur first observed that certain chemical compounds exist in two mirror-image forms, now known as enantiomers. He made these observations while studying the crystallization of sodium ammonium tartrate. Pasteur found that when this compound crystallized, it produced two distinct types of crystals that were mirror images of each other.