diff --git a/oop/object-oriented-programming-quiz.md b/oop/object-oriented-programming-quiz.md
index 9b02320793..180ca0cb02 100755
--- a/oop/object-oriented-programming-quiz.md
+++ b/oop/object-oriented-programming-quiz.md
@@ -532,6 +532,8 @@ public class Tesla extends FlyingCar{}
 public class Honda extends Car{}
 ```
 
+[reference link](https://stackoverflow.com/a/44913313/1573267)
+
 #### Q67. What is the difference between a parameter and an argument?
 
 - [ ] An argument can have many values while a parameter can have only one value.