B. Concentrated sulfuric acid is dissolved in water, which releases a lot of heat, so that the closed gas in the conical bottle is heated and expanded, so that the liquid level on the left side of the U-shaped thin tube drops and the liquid level on the right side rises, so B is correct;
C. concentrated sulfuric acid can absorb water and dehydrate, and the decrease of water leads to the precipitation of white anhydrous CuSO4, so c is correct;
D. Because concentrated sulfuric acid has water absorption, it is impossible to produce blue crystals, so D is wrong.
So choose D.