What will happen to aquatic organisms if solid water were denser than liquid water

Which mantle is under the crust the upper mantle or the lower mantle i think it's upper let me know if i'm right

Ineed to know why d is the correct answer asap

Hydrilla (hydrilla verticillata) is an invasive aquatic plant and one of the most serious aquatic pests in florida. hydrilla has already been introduced to hundreds of bodies of water throughout florida, hydrilla is difficult to control because it grows rapidly and survives in many different water depths and conditions. hydrilla • describe how hydrilla affects native plant and animal species. include both a biotic and an abiotic limiting factor. • suggest one biotic and one abiotic recommendation that could slow the spread of hydrilla