Answer:
a. Labuk does not have a harassment claim based on national origin because these two incidents, although offensive, do not create a hostile work environment.
Step-by-step explanation:
In order for Labuk to have a valid harassment claim, his supervisor must have created an offensive and hostile work environment. Apparently, the supervisor's bad attitude is not shared by Labuk's colleagues, at least it doesn't say so in the question.
The supervisor's attitude might not have been appropriate, but two incidents in 20 years is something can happen to anyone and not just Labuk. Imagine how many times an employee might argue or have some type of dispute with a supervisor during 20 years. Labuk should have reported both incidents to a company's manager.