The function of mordant in the gram staining is to expose grams positive cell to the decolorizer which dissolves the lipids in the cell wall thus allowing the crystals violent-iodine to leach out of the cell. This facilitate the cell subsequently be stained by with safranin.
Answer : The density of the block is estimated to be,
.
Explanation :
Density of the water, 
As we know that,
Buoyant force = 
where,
g = gravitational acceleration
volume of the block = v
density of the block = 
Weight of the Block = Buoyant force exerted by water




Thus, the density of the block is estimated to be,
.
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Because they can live on water and land