Final answer:
The specific gravity of ice for which 90% is submerged in water is 0.9. This represents the submerged fraction of the iceberg's volume that has an equal weight to the water displaced.
Step-by-step explanation:
If 90% of a floating iceberg is underwater, then the specific gravity of the ice is calculated by the volume of ice submerged divided by the total volume of ice. Since specific gravity is the ratio of the density of a substance to the density of a reference substance (usually water for liquids and solids), and given that floating ice has an equal weight to the water it displaces, the specific gravity can be determined by the fraction that is submerged. Given that 90% of the iceberg is underwater, the specific gravity would be 0.9, because that represents the fraction of the iceberg's volume that is equal in weight to the volume of water displaced. Hence, option (b) 0.9 is the correct answer.