Detailed Instructions: This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.
Q: Passage: There are many art galleries in Utrecht. There are also several foundations to support art and artists. Training of artists is done at the Utrecht School of the Arts. The Centraal Museum has many exhibitions on the arts, including a permanent exhibition on the works of Utrecht resident illustrator Dick Bruna, who is best known for creating Miffy ("Nijntje", in Dutch). Although street art is illegal in Utrecht, the Utrechtse Kabouter, a picture of a gnome with a red hat, became a common sight in 2004. Utrecht also houses one of the landmarks of modern architecture, the 1924 Rietveld Schroder House, which is listed on UNESCO's world heritage sites.
A:
What form of art became legal in 2004?