The correctanswer is D hope this helps
B. The sand increases friction by increasing roughness.
Answer:
The mass of the surrounding is 
Explanation:
From the question we are told that
The mass of
is 
The mass of water is 
The chemical equation for the dissociation process is

The specific heat capacity of the mixture is 
The combined mass of the solution is

The mass of the surround here is the mass of the coffee-cup calorimeter and this contain the mixture ( water and the NaOH ) so the mass of the surrounding is

To test if the hypothesis is correct, a good way is to think of it this way:
Density = mass/volume, right?
Calculate the mass and volume of each and do the equation; this will test your hypothesis.
You will be left with the density of each. But, make sure that the sample sizes are the same (controlled variable) otherwise it will be an unfair test.