Which of the following function declaration using default arguments is correct?

Select one:

a$.$ int foo$($int $x=10,$ int $y,$ int $z)$

b$.$ int foo$($int $x=10,$ int $y,$ int $z=10)$

c$.$ int foo $($int $x,$ int $y=5,$ int $z=10)$

d$.$ int foo$($int $x=10,$ int $y=5,$ int $z)$