diff --git a/README.md b/README.md
index 88ff402..0ff7a4c 100644
--- a/README.md
+++ b/README.md
@@ -90,6 +90,7 @@ The majority of the questions were plucked from an [oksoclap](http://oksoclap.co
 function Person(){} var person = Person() var person = new Person()
 ```
 * What's the difference between `.call` and `.apply`?
+* What's the difference between `undefined` and `null`?
 * explain `Function.prototype.bind`?
 * When do you optimize your code?
 * Can you explain how inheritance works in JavaScript?