Question

the density of pure water:
is greater than steel, which is why ships float.
decreases with cooling.
does not change with the addition of salt.
reaches its maximum at about 4o c.

Explanation:

• Analyze each option:
• Option 1: Density of steel is much greater than water. Ships float due to buoyancy from displaced water, not water density > steel. Eliminate.
• Option 2: Water's density increases as it cools until 4°C, then decreases when freezing. So density does not "decrease with cooling" generally. Eliminate.
• Option 3: Adding salt increases water's density (e.g., saltwater is denser than freshwater). So density changes with salt addition. Eliminate.
• Option 4: Pure water's density increases as it cools from room temp to 4°C, reaching maximum at ~4°C, then decreases when cooling below 4°C (toward freezing). This is correct.

Answer:

D. reaches its maximum at about 4°C. (Note: Assuming the "4o C" is a typo for "4°C", the correct option is the one stating water's density reaches maximum at ~4°C.)