Analyze the following code:

```
class Test {
private double i;

public Test(double i) {
this.t();
this.i = i;
}

public Test() {
System.out.println("Default constructor");
this(1);
}

public void t() {
System.out.println("Invoking t");
}
}
```
a. this.t() may be replaced by t().
b. this.i may be replaced by i.
c. this(1) must be called before System.out.println("Default constructor").
d. this(1) must be replaced by this(1.0).

a. this.t() may be replaced by t().
c. this(1) must be called before System.out.println("Default constructor").