Which of the following is an example of disruptive innovation

1. Apple begins selling its up-market iMAC Computer and then it introduces and even more expensive version of the computer with a new screen designed for top quality display

2. A small hamburger stand located in a gas station becomes so popular, that it takes over a large building and takes most of the customers that patronize McDonald's, Wendy and Burger King

3. Amazon announces that it will begin offering electronic books for lower prices on its electronic Kindle reading devices.

4. An upscale department store such as Nordstrom, decides to add a free shopping service for all customers who spend a minimum of $10,000 per year at the store.