What does the author mean by the statement: “As so...

Câu hỏi: What does the author mean by the statement: “As soon as Whistler and Haden began the practice  of signing and numbering their  prints, their work began to increase in value” ?

A The signatures became more valuable than the prints

B Many copies of the prints were made. 

C The prints that were signed and numbered were worth more.

D The signing and numbering of prints was not very popular