Answer: b. ATM is connection-oriented.
Explanation:
From the options given, option A is incorrect. The statement that ATM is a variable-length cell standard that supports voice, video and data is wrong. ATM isn't a variable length cell standard but rather it's a fixed length cell standard.
Option C is incorrect as well as ATM isn't a connectionless network layer protocol similar to IP but rather it is connection oriented which helps in offering predictability regarding latency. In such case, the users are offered quality-of-service.
