(1) In order to make the drinking straw float vertically in the liquid, some metal wires are inserted at the lower end of the straw as counterweights to make the densimeter float vertically in the liquid;

(2) Because the straws float in (a) and (b),

So f float =G,

Water and another liquid have equal buoyancy,

So f float =ρgV row, V row A > V row B,

So ρ water; H=ρ water Hρ liquid; (3) downward; Uneven; (4) Add oil to the container or replace the container with a smaller diameter.