Question

What did Marcel Duchamp contribute to the Dada movement?
b.
He produced many ready-mades, or common objects that are transformed into art.
d.
all of the above

Answer 1

b is correct — Duchamp is best known in Dada for his readymades (ordinary objects presented as art, e.g., Fountain). He also famously challenged the definition of art and influenced conceptual art, so if option d ("all of the above") includes those other true statements, then d would be correct as well.