Given the following type and reference declarations, which assignment is legal?

Select the one correct answer.

(a) obj2 = obj1;

(b) obj3 = obj1;

(c) obj3 = obj2;

(d) I1 a = obj2;

(e) I1 b = obj3;

(f) I2 c = obj1;

// Type declarations: interface Il {} interface 12 {} class C1 implements I1 {} class C2 implements 12 {} class C3 extends C1 implements 12 {} // Reference declarations: C1 obj1 = null; C2 obj2 = null; C3 obj3 = null;