Atwentieth-century sculptor known for exploring open and closed forms in his art is

Henry Spencer Moore

A twentieth-century sculptor known for exploring open and closed forms in his art is Henry Spencer Moore.

Explanation:

Henry Spencer Moore was an important British artist and a celebrated international sculptor in the twentieth century. He was famous for his semi-abstract monumental bronzes which include: drawing analogies between the human body and the landscape which is all over the world. His sculptures are of people with bumpy forms and hollow spaces in their bodies and occasionally, some sculptures used to have holes right through them.

my favorite is blue.

modernism is a 20th century movement