2. How diverse is your workplace? (In terms of race, gender, age, education, or whatever parameters you think are important.)
3. What does your company do to foster diversity, if anything? (Hiring practices, outreach, leadership, internal culture...)
For number three, I think the best way to foster diversity is to practice it. That way it's not empty words, or a checklist item that can be discarded or ignored. By practicing it, I mean value people, value their perspectives and make a conscious decision to include the people and their ideas in your understanding of the company. I think this is difficult as we battle our egos in the context of opposing or competing ideas or perspectives. However, this approach only enriches our understanding, which actually improves our own value to an organization.
If I may suggest a number 4, what about including, "Is diversity a priority, why or why not?"