What is the issue causing less emails to go out?

If I want to introduce a new line of footwear. I am excluding anyone who does not have shoe as an attribute listed in their preference center. I plan to send the emails daily. After a short time, I notice many people updating their preferences, and less emails are going out.

What is the issue causing less emails to go out?
A . Preference center is too strict.
B . High Watermark if journey builder.
C . Email frequency too high.
D . Deliverability issues on account.

Answer: B