We have the following figure:
we have that the cover has dimensions of 15 feet by 30 feet, then the area that can cover is the following:
[tex]A_c=15\cdot30=450ft^2[/tex]while the area of the pool is the following:
[tex]A_p=(20)(20)=400ft^2[/tex]clearly we have that the area of the pool cover is greater than the area of the pool, therefore, the cover will protect the entire pool (option B)