Answer:
Post advertisements on social media and message the subscribers.
Step-by-step explanation:
There is no point in not promoting and putting forward the work that he has been doing. All of the given options are about promoting the content but Sam needs to choose the ones which are efficient and seem professional as well.
Posting advertisements about the website promotes the content on a wider base and helps in luring more and more people to the website.
Messaging or sending an email to the subscribers is a healthy of letting the subscribers about the updates and latest posts.