The answer is C because you have to find acceleration.
Given :
Length , l = 59.8 m.
Breadth , b = 26.6 m.
Depth , d = 3.7 ft .
Density of water ,
.
To Find :
Mass of water in pool .
Solution :
First we will covert depth into m from ft .

For ,

So , volume of pool is :

We know , density is given by :

So , 
Putting given values in above equation :

Hence , this is the required solution.
The answer to that question is B