What can be inferred about the grandmother mentioned in the text?

The conclusion that the grandmother is the hardest working individual known to the speaker suggests a deep admiration and respect for her work ethic. This assessment implies that her commitment and effort in her various responsibilities have made a significant impression on the speaker, indicating that she consistently exhibited a strong sense of diligence throughout her life. This understanding hinges on the idea that the speaker views her more favorably compared to others, which reinforces the notion that her tenacity and perseverance are noteworthy and perhaps unparalleled in the speaker's experiences or observations.

The other choices do not align with this interpretation. They each suggest lesser degrees of hard work or imply a lack of work, which contradicts the idea of her being revered as exceptionally hardworking. Thus, the answer that positions her as the hardest working individual encapsulates the admiration that likely informs the speaker’s viewpoint.