Final answer:
The most credible source for an essay on the wage gap between men and women is a university study that includes a large sample size and business trend data, published in an academic journal. Hence the correct answer is option 3- 'A university study published in an academic journal sampling 1,835 adults conducted in 2015 combined with statistical data on business trends over time'.
Step-by-step explanation:
When writing an essay on the gap in wages between men and women, the most credible source would be a university study published in an academic journal that samples a large number of adults and combines this with statistical data on business trends over time. This option, involving a study sampling 1,835 adults conducted in 2015, not only includes a significant sample size but also appears to be more comprehensive, including statistical trends which enhance the credibility of the data. Furthermore, academic journals typically have rigorous peer-review processes that ensure the quality and reliability of the information presented.