A、About 40. B、Almost 200. C、Over 240. D、More than 72. B根据原文，Smithsonian展览展出了约200件Joseph Cornell作品，所以答案为B。

You could say that Joseph Cornell became an artist because of his love of collecting. Cornell used to spend his free time exploring the street life of New York City in the 1920s. He soon started collecting old books, prints, postcards and even three-dimensional objects that he found in stores that sold used books.
     Cornell also attended many museum shows, gallery openings and dance performances. He was influenced by a group of artists called the Surrealists who combined images in unusual and often strange ways.
     Joseph Cornell started making his own works by cutting out different pictures and putting them together in creative and magical combinations. Soon, he started making boxes inside of which were carefully arranged pictures and objects. He worked on his art at night after finishing his day job. Later, when his boxes and images started selling and receiving public recognition, he worked on his art full time.
    Joseph Cornell died in 1972. The Smithsonian exhibit showed almost two hundred works made during his forty-year career, one work is called "Soap Bubble Set". A box with a glass window shows a map of the moon, several pictures of sea creatures, two glass cups and two white pipes for smoking. In another box, Cornell combines an image of a cockatoo bird with a music box and watch faces.
    Joseph Cornell once said his art was based on everyday experiences. He said that with his art he showed "the beauty of the commonplace". Visitors who came to this special exhibit found magic in regular objects-and even saw beauty in a box.