We have been given that C represents number of stamps collected by Callie.
Therefore, twice the number of stamps that Callie collects = 2C
Now, it has been given that Jenna has 20 less than twice the number of stamps that Callie has.
Therefore, the number of stamps that Jenna has is given by
![2C-20](https://img.qammunity.org/2019/formulas/mathematics/high-school/50djea7962afnxiubgxy3obx9zkspdxcr5.png)
Therefore, the expression 2C - 20 represents the number of stamps that Jenna has.
b is the correct option.