In the following code, which line will cause a compiler error?

```
Line 1 public class ClassA
Line 2 {
Line 3 public ClassA() {}
Line 4 public int method1(int a){}
Line 5 public final int method2(double b){}
Line 6 }
Line 7 public ClassB extends ClassA
Line 8 {
Line 9 public ClassB(){}
Line 10 public int method1(int b){}
Line 11 public int method2(double c){}
Line 12 }

```

a. Line 4 b. Line 5 c. Line 10 d. Line 11

d. Line 11