Answer: A.
.
Step-by-step explanation:
- A difference of squares problem is factored as :

- For this both terms in the form of squares and a minus sign between them.
From all the options only option A has both terms square and they minus sign between them.
Also, 
Here a= 3x and b= 4
Hence, the correct answer is A.
.
The diameter is the cross section of the widest part of a sphere.
The two lines are perpendicular because both of the lines intersects