The correct answer is B. Acting as mother or father.
Step-by-step explanation
The term in loco parentis is a word of Latin origin used to refer to the expression "in the place of a father/mother" and refers to the responsibility that a person or organization assumes as a father or mother. Therefore, it is correct to say that Stella and Thane took on the role of father/mother with Gretchen because the paragraph says that "the couple walked her through the process of purchasing a car. They often invited her over for holidays, and Gretchen I was grateful to them for their advice. " So the correct answer is B. Acting as mother or father.