Step 1: Define the Neo-Classical era in sculpture. It was a movement in the late 18th and early 19th centuries that drew inspiration from the "classical" art of ancient Greece and Rome, emphasizing order, clarity, and idealism.
Step 2: Classify the artists by their period.
(A) Antonio Canova (1757-1822): The most famous and quintessential sculptor of the Neo-Classical period.
(B) John Flaxman (1755-1826): A leading English sculptor and draughtsman of the Neo-Classical movement.
(C) Bertel Thorvaldsen (1770-1844): A Danish sculptor who was, along with Canova, a leader of the Neo-Classical style in Rome.
(D) Gianlorenzo Bernini (1598-1680): The dominant figure of the Italian Baroque period, known for dramatic and emotive works.
(E) Francois Duquesnoy (1597-1643): A Flemish sculptor active in Rome, associated with the Baroque style, though with more classicizing tendencies than Bernini.
Step 3: Group the Neo-Classical sculptors. The artists who belong to the Neo-Classical era are Canova, Flaxman, and Thorvaldsen. This corresponds to (A), (B), and (C).