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