Which of the following conditions must be present to make pixel$-$based product retargeting possible?

a$.$

The target audience member has given express consent by providing an email address or other contact information.

b$.$

The target audience member visited at least three pages on the marketer's site.

c$.$

The target audience member has purchased directly from the marketer's site in the past.

d$.$

The target audience member has not cleared past browsing behavior data collected by cookies.