Choice D is correct. It is given that the density of the object is less than or equal to 1.5 grams per milliliter, so the inequality below describes the density of the object.

density≤1.5

Because density is equal to mass divided by volume, the inequality above can be rewritten as mass/volume≤1.5

The volume of the water displaced by the object is equal to the volume of the object. Also, m represents the mass of the object. Substituting 10.5 for volume and m for mass results in the following inequality: m/10.5≤1.5

To determine the values of m that satisfy the inequality, multiply both sides of the inequality by 10.5. The resulting inequality is m≤15.75.

Therefore, the mass of the object must be less than or equal to 15.75 grams. The correct answer is: m≤15.75.