According to Archimedes principle, the buoyancy of the nail ball is: F nail = ρ water gV row;
Buoyancy of ball B: F B = ρ water gV ranks second, so F A < F B.
Because the two containers are exactly the same, let the cross-sectional area be s, because row A is smaller than row B.
According to the formula △h=V row S, it can be determined that the rising height of water in the container where ball A is located is smaller than that of water in the container where ball B is located;
Because the original water levels in the two containers are the same, the depth of water in container B is now greater than that in container A. According to the characteristics of liquid pressure, the deeper the depth, the greater the pressure, so it can be determined that P A < P B.
To sum up, the choice is: ad.