Answer:
How is your new job? Are you enjoying it. Is correct!
How is your new job? Are you knowing it. (doesn't make since)
How is your new job? Are you known it. (Doesn't make since, and refers to past tense, which the passage is present tense.)
How is your new job? Are you enjoyed it. (Refers to past tense, which the passage is present tense.)
Step-by-step explanation:
Hope it helps! =D