Answer: You can add a chat window for support.
Explanation:
The answer above is a well known feature in well-made web apps and the only difference between apps and static email advertisements in the options.
Both the apps and the email advertisement work to advertise a product so option A is incorrect.
You can also integrate images and text related to your brand in both the app and email.
Both of them enable you to reach more people as well.
Option B is therefore correct.
