Answer:
event based and time based
Explanation:
OTP tokens come in two types: event-based (HOTP) and time-based (TOTP). Event-based OTP tokens generate new codes at the press of the button and the code is valid until it is used by the application. Time-based OTP tokens generate codes that are valid only for a certain amount of time (eg, 30 or 60 seconds), after which a new code must be generated
