Which of the following could result in women being paid less than men? a. Women preferring to work in safer working conditions b. Women entering and leaving the labor force to care for children c. Women obtaining less human capital because they don't plan to work continuously to the age of retirement d. All of the answer choices are correct.

Let's analyze each option: 1. **Option a: Women preferring to work in safer working conditions.** If women choose jobs with safer (and possibly less hazardous) conditions, these jobs might have lower compensation compared to riskier positions that often offer higher wages to compensate for the risk. This can contribute to lower average wages. 2. **Option b: Women entering and leaving the labor force to care for children.** Interruptions in career due to caregiving responsibilities can lead to reduced work experience, fewer opportunities for career advancement, and slower accumulation of job-specific skills, all of which can lower lifetime earnings. 3. **Option c: Women obtaining less human capital because they don't plan to work continuously to the age of retirement.** Continuous work experience often results in greater skill development and higher productivity, which in turn increases earning potential. If women accumulate less human capital by planning shorter careers, this could result in relatively lower wages. Since each of the options can contribute to situations where women might be paid less than men, the correct answer is: \( \textbf{d. All of the answer choices are correct.} \)