(1) When the liquid is transferred to the experimental device as shown in figure 1, the deeper the liquid is, the more obvious the rubber film on the side wall protrudes, which can be used to explore the relationship between the internal pressure and depth of the liquid;

(2) Each unit of the spring dynamometer represents 0.5N, so the indicated value of the dynamometer is 3n;

Let each cell of the lever be L, the pulling force of the spring dynamometer be power, and the gravity of the hook code be resistance, which is hung in nL.

According to the equilibrium condition of lever F 1L 1=F2L2,

3N×L= 1N×nL，

n=3，

Therefore, the hook code hangs in the.

So the answer is: depth; A.