The code (cleaned up) is:

int x = 0;
int f() { return x; }
int g() { int x = 1; return f(); }
int main() { printf("%d", g()); }

C uses static (lexical) scoping. Inside f(), the name x refers to the global x, which is 0. The local x = 1 inside g() is not visible to f().

So g() returns f() = 0, and the output is 0.

Answer: (B) 0