Concept:Obstructing data in transmission means stopping or disrupting the flow of data, which is an interruption attack.Explanation:Interruption is a data threat where an attacker blocks or obstructs data from reaching its intended destination, making the system or network unavailable.This affects the availability of data.Fabrication creates fake data, interception reads or listens to data, and modification changes data.Therefore, obstructing data in transmission is called interruption.Answer:B. interruption