∴ their buoyancy f 1 > F2,

∫A sinks and B hangs.

∴G A > F 1，G B =F2。

∴G a > g b，

(2)∫A sink, B float, C float,

∴ ρ A > ρ 1，ρ B =ρ2，ρ C < ρ 3

∵ρ 1=ρ2>ρ3,

∴ ρ A >ρB >ρC，

(3)∵V B > V C, as can be seen from the figure, V B > V C.

∵ ρ 2 >ρ3.

Their buoyancy F2 > F3, both balls float, and their buoyancy is equal to their own gravity.

∴G b > British c,

∴G A > uk b > uk c,

So choose ad.