I am completely stuck on this one...

Let z(x,y) = 3xy^2 - 2y + 5x^2y^2

the last term should read "5 x sq y sq"

Which of the following is equal to a^z/ax^2?

my options are

10y^2

(3y^2 + 10xy^2)^2

6y + 20xy

3y^2 + 10xy^2

6x + 10x^2

one of these is right, but i'm not sure which, or how...any help would be great!