We can see here that the type of biased language that can be found in Line 3 is: c. ethnicity.
The statement "I think he gypped some of my tips from last night" contains a biased and offensive term. The word "gypped" is a derogatory term derived from the word "gypsy," which is considered an ethnic slur against Romani people. It reveals negative stereotypes associated with the Romani community, implying dishonesty or swindling.
Biased language refers to words or phrases that demonstrate prejudice, stereotypes, or unfairness towards particular groups of people based on characteristics such as race, ethnicity, gender, sexual orientation, religion, age, disability, socioeconomic status, or other factors.