Which of the following sentences is free of any gender, nationality, age, or race bias?

Option D is free of bias, as it describes an individual’s attributes (hardworking, excels in science) without stereotyping based on gender, nationality, age, or race. Option A uses “firemen,” a gender-specific term, implying exclusion of women. Option B uses “his,” assuming a male subject, introducing gender bias. Option C specifies “young,” indicating age bias, and “man,” suggesting gender bias. This question tests workplace communication ethics under the Communication and Career Development category.