(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.