The term "active digital footprint" refers to the information that you intentionally share and leave behind while interacting online. Based on this definition, the option that contributes to your active digital footprint is:
B) personal info you intentionally enter into a secure website when making a purchase.
This is because it is data that you actively provide during your online activities. The other options (A, C, and D) generally refer to passive data collection or information that you did not actively submit.