How should the quantity of required Identity Verification Credits be estimated?

Northern Trail Outfitters (NTO) is planning to build a new customer service portal and wants to use password less login, allowing customers to login with a one-time passcode sent to them via email or SMS.

How should the quantity of required Identity Verification Credits be estimated?
A . Each community comes with 10,000 Identity Verification Credits per month and only customers with more than 10,000 logins a month should estimate additional SMS verifications needed.
B . Identity Verification Credits are consumed with each SMS (text message) sent and should be estimated based on the number of login verification challenges for SMS verification users.
C . Identity Verification Credits are consumed with each verification sent and should be estimated based on the number of logins that will incur a verification challenge.
D . Identity Verification Credits are a direct add-on license based on the number of existing member-based or login-based Community licenses.

Answer: B