You can spend $5 for lunch and you would like to have two double cheeseburgers. When you get to the restaurant, you find out the price for double cheeseburger has increased from $2.50 to $2.99. You decide to have just one double cheeseburger for lunch. This is best described as a(n):
A. substitution effect.
B. income effect.
C. buyer's reservation price effect.
D. seller's reservation price effect.