Final answer:
In a thick smoothie, you may need to charge extra for frozen strawberries, blueberries, and raspberries.
Step-by-step explanation:
In a thick smoothie, if strawberries, blueberries, and raspberries are the only frozen fruits, they may need to be charged extra.
For example, if a customer wants a smoothie with only frozen strawberries, blueberries, and raspberries, the extra charge might be applied because these fruits are more expensive when purchased frozen compared to other fruits.
Therefore, the correct option is a) Strawberries, blueberries, and raspberries.